Js substring starting from character. Multiline lines and newline

This article will talk about what is strings in JavaScript and methods of working with them.

Strings are simply groups of characters, such as "JavaScript", "Hello world!" ", "http://www.quirksmode.org" or even "14". To program in JavaScript, you need to know what strings are and how to work with them, since you will need to use them very often. Many things such as URL pages, values CSS parameters and form input elements are all strings.

First I'll try to explain working with strings, then the difference between in JavaScript. Even if you have programming experience in another language, read this part carefully. At the end I will talk about the most important strings in JavaScript.

String Basics

Let's look at the basics of working with strings in JavaScript.

Using quotes

When you announce strings in JavaScript or work with them, always enclose them in single or double quotes. This tells the browser that it is dealing with a string. Do not mix the use of quotes in your code; if you start a line with a single quote and end with a double quote, JavaScript will not understand what you meant. Typically, I use single quotes when working with strings, since I chose to use double quotes for HTML and single quotes for JavaScript. Of course, you can do everything differently, but I advise you to come up with a similar rule for yourself.

Let's imagine two lines that we will use throughout the article:

Var a = "Hello world!"; var b = "I am a student.";

We have now declared two variables, "a" and "b", and assigned them string values. After that we can work with them, but first we will solve one problem: let's say I wrote:

Var b = "I"m a student.";

The string contains an extra single quote, and JavaScript thinks the string is complete and displays an error message without understanding what comes next. Therefore you need escape quote, telling the browser to treat it as a character and not as a line ending. This is done using a backslash before the quote:

Var b = "I\"m a student.";

Note that you can insert double quotes into a string without escaping them. Since you are using single quotes to start and end the string,

Var b = "I\"m a "student".";

perceived without problems. Double quotes are automatically treated as part of a string, not a command.

Built-in functions

Once the strings have been defined, you can start using them. For example, you can concatenate one string to another, or take a substring from the string “b” consisting of the second to fourth characters and insert them into the middle of the string “a”, or determine which character is the twelfth in “a”, how many characters are in “b”, whether they contain the letter “ q" etc.

To do this, you can use the built-in functions that JavaScript predefines for each line. One of them, “length,” returns the length of the string. That is, if you want to calculate the length of “Hello world!”, write:

Var c = "Hello world!".length;

Previously, we assigned this string to the variable "a". Thus, you have made the variable "a" a string, so the "length" function can also be applied to it, and the following operation will give the same result:

Var c = a.length;

Remember that you can use "length" for any string - it's a built-in function. You can calculate the length of any string, for example: "location.href" or "document.title" or declared by you.

Below I will present a list of common built-in methods and properties.

Strings and numbers

Some programming languages ​​require you to specify whether a variable is a number or a string before doing anything else with it. JavaScript is easier refers to the difference between strings and numbers. In fact, you can even add numbers with strings:

Var c = a + 12;

In some programming languages, processing such a string will result in an error. After all, “a” is a string, and “12” is a number. However, JavaScript tries to solve the problem by assuming that "12" is also a string. Thus "c" becomes "Hello world!12". This means that if you use "+" with a string and a number, JavaScript tries to make the number a string. If you use mathematical operations to a string, JavaScript tries to turn it into a number. If it is not possible to convert a string to a number (for example, due to the presence of letters in it), JavaScript returns NaN - “Not a Number - is not a number.”

Finally, in JavaScript there is no difference between integers and floating point numbers.

Number → string

For number to string conversion enter:

Var c = (16 * 24) / 49 + 12; d = c.toString();

You can then apply all string methods to "d" and "c" still contains a number.

String → number

If you want to convert a string to a number, first make sure it consists of only characters 0-9. To do this I simply multiply the string by 1.

Var c = "1234"; d = c * 1;

Since multiplication only works with numbers, JavaScript turns the string into a number if possible. Otherwise, the result is NaN.

Note that if you write:

Var c = "1234"; d = c + 0;

The result will be "12340" because JavaScript uses "+" to concatenate strings rather than adding them.

String Properties and Methods

So what can we do with strings? Association is a special case, but all other commands (methods) can be used with any string using the construct:

String_name.method();

List of built-in JavaScript methods for working with strings

Concatenation - joining strings

First, you can concatenate strings by adding them together, like this:

Document.write(a + b);

the result will be: “Hello world!I am a student.” " But of course you want there to be space between sentences. To do this, write the code as follows:

Document.write(a + " " + b);

So we will connect three strings: “a”, ““”” (one space) and “b”, resulting in: “Hello world!” I am a student. »

You can even use numbers or calculations, for example:

Document.write(a + 3 * 3 + b);

Now we concatenate the string “a”, then the result of the expression “3 * 3”, considered as a string, and “b”, getting: “Hello world!9 I am a student. »

You need to be careful when using addition. Team

Document.write(a + 3 + 3 + b);

connects 4 strings: "a", "3", "3" and "b" because "+" in in this case means “to join the lines”, not “to add” and the result is: “Hello world!33 I am a student. " If you want to add 3 and 3 before creating a string, use parentheses.

Document.write(a + (3 + 3) + b);

This expression connects the string “a”, the result of the expression “3 + 3” and “b”, resulting in: “Hello world!6 I am a student. "

indexOf

One of the most widely used built-in methods is "indexOf". Each character has its own index containing the number of its position in the line. Note that the index of the first character is 0, the second is 1, etc. Thus, the index of the character “w” in the string “a” is 6.

Using "indexOf" we can output the index of a character. Write ".indexOf(" ")" after the line name and insert the character you are looking for between the quotes. For example:

Var a = "Hello world!"; document.write(a.indexOf("w"));

will return 6 . If a character occurs multiple times, this method returns the first occurrence. That is

Document.write(a.indexOf("o"));

will return 4 because it is the index of the first "o" in the string.

You can also search for a combination of symbols. (Of course, this is also a string, but to avoid confusion, I won't call it that). "indexOf" returns the position of the first character of the combination. For example:

Document.write(a.indexOf("o w"));

will also return 4 because it is the index of "o".

Moreover, it is possible to search for a character after a certain index. If you enter

Document.write(a.indexOf("o", 5));

then you will get the index of the first “o” following the character with index 5 (this is a space), that is, the result will be 7 .

If the character or combination does not occur in the string, "indexOf" will return "-1". This is essentially the most popular use of "indexOf": checking for existence certain combination characters. It is the core of the script that defines the browser. To define IE you take the line:

Navigator.userAgent;

and check if it contains "MSIE":

If(navigator.userAgent.indexOf("MSIE") != -1) ( //Any actions with Internet Explorer }

If the index of "MSIE" is not "-1" (if "MSIE" occurs anywhere in the line), then current browser- I.E.

lastIndexOf

There is also a "lastIndexOf" method that returns the last occurrence of a character or combination. It does the opposite of "indexOf". Team

Var b = "I am a student."; document.write(b.lastIndexOf("t"));

will return 13 because it is the index of the last "t" in the string.

charAt

The "charAt" method returns the character at the specified position. For example, when you enter

Var b = "I am a student."; document.write(b.charAt(5));

the result is "a" since it is the character in sixth position (remember that the index of the first character starts at 0).

length

The "length" method returns the length of the string.

Var b = "I am a student."; document.write(b.length);

will return "15". The length of the string is 1 greater than the index of the last character.

split

"split" is special method, which allows you to split a string by certain characters. Used when the result needs to be stored in an array rather than in a simple variable. Let's split "b" by spaces:

Var b = "I am a student." var temp = new Array(); temp = b.split(" ");

Now the string is split into 4 substrings, which are placed in the "temp" array. The spaces themselves have disappeared.

Temp = "I"; temp = "am"; temp = "a"; temp = "student";

The "substring" method is used to subtract part of a string. Method syntax: ".substring(first_index, last_index)". For example:

Var a = "Hello world!"; document.write(a.substring(4, 8));

will return "o wo", from the first "o" (index 4) to the second (index 7). Note that "r" (index 8) is not part of the substring.

You can also write:

Var a = "Hello world!"; document.write(a.substring(4));

This will give the whole substring "o world! ", starting from the character with index 4 to the end of the line.

substr

There is also a "substr" method that works a little differently. It does not use the index number as the second argument, but the number of characters. That is

Document.write(a.substr(4, 8));

returns 8 characters, starting from the character at index 4 (“o”), that is, the result is: “ o world! »

toLowerCase and toUpperCase

Finally, 2 methods that may sometimes be useful to you: “toLowerCase” converts the entire string to lower case, and “toUpperCase” converts it to upper case.

Var b = "I am a student."; document.write(b.toUpperCase());

As a result, we get “I AM A STUDENT. "

From the author: Greetings, friends. In several previous articles, we got acquainted with the numeric data type in JavaScript and worked with numbers. Now it's time to work with strings in JavaScript. Let's take a closer look at the string data type in JavaScript.

We have already briefly become acquainted with the string type and, in fact, we only learned what a string is and how it is written. Let's now take a closer look at strings and methods for working with them.

As you remember, any text in JavaScript is a string. The string must be enclosed in quotes, single or double, it makes no difference:

var hi = "hello", name = "John";

var hi = "hello" , name = "John" ;

Now we have written only one word into the variables. But what if we want to record a large amount of text? Yes, no problem, let's write some fish text into a variable and output it to the console:

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit. Quos nisi, culpa exercitationem!"; console.log(text);

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit. Quos nisi, culpa exercitationem!"; console. log(text);

Works. But if there is a lot of text, we will probably have line breaks to start with new paragraph a new line. Let's try adding a line break like this to our text:

As you can see, my text editor already highlighted in red possible problem. Let's see how the browser reacts to a line break in this interpretation:

Syntax error, as expected. How to be? There are several ways to store multiline text in a variable. You might have already guessed about one of them, we're talking about about string concatenation:

As you can see, the editor already reacts normally to this option of writing a string to a variable. Another option is to use the backslash (\), which in JavaScript and many other programming languages ​​is an escape character that allows you to safely work with special characters. We will learn what special characters are further. So, let's try to escape the invisible newline character:

Shielding also solved our problem. However, if we look at the console, both string concatenation and line feed escaping, while solving the problem of writing to the program, did not solve the problem of displaying a multiline string on the screen. Instead of a multi-line line, we will see one-line text in the console. What should I do?

And here it will help us special character new line - \n. By adding this special character to the line in the right place, we will tell the interpreter that it is necessary to terminate at this place current line and make a new line.

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit.\nQuos nisi, culpa exercitationem!"; console.log(text);

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit.\ "Quos nisi, culpa exercitationem!"; console. log(text);

Actually, if you don’t mind writing the text in the code in one line, then we can do it like this:

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit.\nQuos nisi, culpa exercitationem!"; console.log(text);

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit.\nQuos nisi, culpa exercitationem!"; console. log(text);

The result on the screen will not change; we will see multi-line text in the browser console:

We really don’t really need the backslash escape character in the code in this situation. But it is actually needed, as noted above, for escaping special characters. For example, inside a string that we enclosed in single quotes, there is an apostrophe, i.e. single quote:

var text = "Lorem ipsum d"olor sit amet";

As semantic “frameworks” for the use of functions and constructions for processing strings, they are of particular interest for programming information processing processes according to its semantic content. On JavaScript functions for working with strings can be combined into their own semantic constructs, simplifying the code and formalizing the subject area of ​​the task.

In the classical version, information processing is, first of all, string functions. Each function and construct of the language has its own characteristics in the syntax and semantics of JavaScript. The methods for working with strings here have their own style, but in common use it is just syntax within simple semantics: search, replace, insertion, extraction, connotation, change case...

Description of string variables

To declare a string, use the construction var. You can immediately set its value or generate it during the execution of the algorithm. You can use single or double quotes for a string. If it must contain a quotation mark, it must be escaped with the "\" character.

The line indicated requires escaping internal double quotes. Likewise, the one marked with single quotes is critical to the presence of single quotes inside.

In this example, the string "str_dbl" lists useful special characters that can be used in the string. In this case, the “\” character itself is escaped.

A string is always an array

JavaScript can work with strings in a variety of ways. The language syntax provides many options. First of all, one should never forget that (in the context of the descriptions made):

• str_isV => "V";
• str_chr => """;
• str_dbl => "a".

That is, the characters in a string are available as array elements, with each special character being one character. Escaping is an element of syntax. No “screen” is placed on the actual line.

Using the charAt() function has a similar effect:

• str_isV.charAt(3) => "V";
• str_chr.charAt(1) => """;
• str_dbl.charAt(5) => “a”.

The programmer can use any option.

Basic String Functions

In JavaScript it is done a little differently than in other languages. The name of the variable (or the string itself) is followed by the name of the function, separated by a dot. Typically, string functions are called methods in the style of language syntax, but the first word is more familiar.

The most important method of a string (more correctly, a property) is its length.

• var xStr = str_isV.length + "/" + str_chr.length + "/" + str_dbl.length.

Result: 11/12/175 according to the lines of the above description.

The most important pair of string functions is splitting a string into an array of elements and merging the array into a string:

• split(s [, l]);
• join(s).

In the first case, the string is split at the delimiter character “s” into an array of elements in which the number of elements does not exceed the value “l”. If the quantity is not specified, the entire line is broken.

In the second case, the array of elements is merged into one line through a given delimiter.

A notable feature of this pair: splitting can be done using one separator, and merging can be done using another. In this context in JavaScript work with strings can be "taken outside" the syntax of the language.

Classic string functions

Common string processing functions:

• search;
• sample;
• replacement;
• transformation.

Represented by methods: indexOf(), lastIndexOf(), toLowerCase(), toUpperCase(), concan(), charCodeAt() and others.

In JavaScript, working with strings is represented by a large variety of functions, but they either duplicate each other or are left for old algorithms and compatibility.

For example, using the concat() method is acceptable, but it is easier to write:

• str = str1 + str2 + str3;

Using the charAt() function also makes sense, but using charCodeAt() has a real effect practical significance. Similarly, for JavaScript, a line break has a special meaning: in the context of displaying, for example, in an alert() message, it is “\n”, in a page content generation construct it is “
" In the first case it is just a character, and in the second it is a string of characters.

Strings and Regular Expressions

In JavaScript, working with strings includes a regular expression mechanism. This allows complex searches, fetching, and string conversions to be performed within the browser without contacting the server.

Method match finds, and replace replaces the found match the desired value. Regular expressions are implemented in JavaScript in high level, in essence, are complex, and due to the specifics of the application, they transfer the center of gravity from the server to the client’s browser.

When applying methods match, search And replace not only should due attention be paid to testing across the entire spectrum acceptable values initial parameters and search strings, but also evaluate the load on the browser.

Regular expression examples

The scope of regular expressions for processing strings is extensive, but requires great care and attention from the developer. First of all, regular expressions are used when testing user input in form fields.

Here are functions that check whether the input contains an integer (schInt) or a real number (schReal). The following example shows how efficient it is to process strings by checking them for only valid characters: schText - text only, schMail - correct address Email.

It is very important to keep in mind that in JavaScript, characters and strings require increased attention to locale, especially when you need to work with Cyrillic. In many cases, it is advisable to specify the actual character codes rather than their meanings. This applies primarily to Russian letters.

It should be especially noted that it is not always necessary to complete the task as it is set. In particular, with regard to checking integers and real numbers: you can get by not with classical string methods, but conventional designs syntax.

Object-Oriented Strings

In JavaScript, working with strings is represented by a wide range of functions. But this is not a good reason to use them in their original form. The syntax and quality of the functions are impeccable, but it is a one-size-fits-all solution.

Any use of string functions involves processing the real meaning, which is determined by the data, the scope, specific purpose algorithm.

The ideal solution is always to interpret data for its meaning.

By representing each parameter as an object, you can formulate functions to work with it. We are always talking about processing symbols: numbers or strings are sequences of symbols organized in a specific way.

There are general algorithms, and there are private ones. For example, a surname or house number are strings, but if in the first case only Russian letters are allowed, then in the second case numbers, Russian letters are allowed, and there may be hyphens or indices separated by a slash. Indexes can be alphabetic or numeric. The house may have buildings.

It is not always possible to foresee all situations. This important point in programming. It is rare that an algorithm does not require modification, and in most cases it is necessary to systematically adjust the functionality.

Formalization of the processed line information in the form of an object improves the readability of the code and allows it to be brought to the level of semantic processing. This is a different degree of functionality and significantly best quality code with greater reliability of the developed algorithm.

There are several ways to select substrings in JavaScript, including substring(), substr(), slice() and functions regexp.

In JavaScript 1.0 and 1.1, substring() exists as the only simple way to select part of a larger string. For example, to select the line press from Expression, use "Expression".substring(2,7). The first parameter to the function is the character index at which the selection begins, while the second parameter is the character index at which the selection ends (not including): substring(2,7) includes indexes 2, 3, 4, 5, and 6.

In JavaScript 1.2, functions substr(), slice() And regexp can also be used to split strings.

Substr() behaves in the same way as substr the Pearl language, where the first parameter indicates the character index at which the selection begins, while the second parameter specifies the length of the substring. To perform the same task as in the previous example, you need to use "Expression".substr(2,5). Remember, 2 is the starting point, and 5 is the length of the resulting substring.

When used on strings, slice() behaves similarly to the function substring(). This is, however, much more powerful tool, capable of functioning with any type of array, and not just strings. slice() also uses negative offsets to access desired position, starting from the end of the line. "Expression".slice(2,-3) will return the substring found between the second character and the third character from the end, returning again press.

Latest and most universal method for working with substrings - this is working through regular expression functions in JavaScript 1.2. Once again, paying attention to the same example, the substring "press" obtained from the string "Expression":

Write("Expression".match(/press/));

Built-in object String

An object String This is an object implementation of a primitive string value. Its constructor looks like:

New String( meaning?)

Here meaning any string expression that specifies the primitive value of an object. If not specified, the object's primitive value is "" .

Properties of the String object:

constructor The constructor that created the object. Number of characters per line. prototype A reference to the object class prototype.

Standard String Object Methods

Returns the character at the given position in the string. Returns the code of the character located at a given position in the string. Returns a concatenation of strings. Creates a string from characters specified by Unicode codes. Returns the position of the first occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. Compares two strings based on language operating system. Matches a string against a regular expression. Matches a string against a regular expression and replaces the found substring with a new substring. Matches a string with a regular expression. Retrieves part of a string and returns a new string. Splits a string into an array of substrings. Returns a substring given by position and length. Returns a substring specified by the starting and ending positions. Converts all letters of a string to lowercase, taking into account the operating system language. Converts all letters in a string to uppercase based on the operating system language. Converts all letters in a string to lowercase. Converts an object to a string. Converts all letters in a string to uppercase. Returns the primitive value of the object.

Non-standard methods of the String object

Creates HTML bookmark (…). Wraps a string in tags …. Wraps a string in tags …. Wraps a string in tags …. Wraps a string in tags …. Wraps a string in tags …. Wraps a string in tags …. Wraps a string in tags …. Creates HTML hyperlink (…). Wraps a string in tags …. Wraps a string in tags …. Wraps a string in tags . Wraps a string in tags .

length property

Syntax : an object.length Attributes: (DontEnum, DontDelete, ReadOnly)

Property value length is the number of characters in the line. For an empty string this value is zero.

anchor method

Syntax : an object.anchor( Name) Arguments: Name Result: string value

Method anchor object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to create a bookmark in an HTML document with the specified name. For example, the operator document.write("My text".anchor("Bookmark")) is equivalent to the operator document.write(" My text") .

big method

Syntax : an object.big() Result: string value

Method big returns a string consisting of object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text large print. For example, the statement document.write("My text".big()) will display the string My text on the browser screen.

blink method

Syntax : an object.blink() Result: string value

Method blink returns a string consisting of a primitive string value object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in blinking font. The specified tags are not included in HTML standard and are only supported by Netscape and WebTV browsers. For example, the statement document.write("My text".blink()) will display the string My text on the browser screen.

bold method

Syntax : an object.bold() Result: string value

Method bold returns a string consisting of a primitive string value object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in bold font. For example, the operator document.write("My text".bold()) will display the line My text .

charAt method

Syntax : an object.charAt( position) Arguments: position any numeric expression Result: string value

Method charAt returns a string consisting of the character located in the given positions primitive string value object. Line character positions are numbered from zero to an object. -1. If the position is outside this range, an empty string is returned. For example, the statement document.write("String".charAt(0)) will print the character C to the browser screen.

charCodeAt method

Syntax : an object.charCodeAt( position) Arguments: position any numeric expression Result: numeric value

Method charAt returns a number equal to the Unicode code of the character located in the given positions primitive string value object. Line character positions are numbered from zero to an object. -1. If the position is outside this range, it returns NaN. For example, the operator document.write("String".charCodeAt(0).toString(16)) will display the hexadecimal code of the Russian letter "C" on the browser screen: 421.

concat method

Syntax : an object.concat( line0, line1, …, stringN) Arguments: line0, line1, …, stringN any string expressions Result: string value

Method concat returns a new string that is the concatenation of the original string and the method arguments. This method is equivalent to the operation

an object + line0 + line1 + … + stringN

For example, the operator document.write("Frost and sun.".concat("Wonderful day.")) will display the line Frost and sun on the browser screen. It's a wonderful day.

fixed method

Syntax : an object.fixed() Result: string value

Method fixed returns a string consisting of a primitive string value object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in a teletype font. For example, the statement document.write("My text".fixed()) will display the string My text on the browser screen.

fontcolor method

Syntax : an object.fontcolor(color) Arguments: color string expression Result: string value

Method fontcolor returns a string consisting of a primitive string value object, enclosed in tags color>…. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in a specified color. For example, the statement document.write("My text".fontcolor("red")) will display the string My text on the browser screen.

fontsize method

Syntax : an object.fontsize( size) Arguments: size numeric expression Result: string value

Method fontsize returns a string consisting of a primitive string value object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in a specified font size. For example, the statement document.write("My text".fontsize(5)) will display the string My text on the browser screen.

fromCharCode method

Syntax : String.fromCharCode( code1, code2, …, codeN) Arguments: code1, code2, …, codeN numeric expressions Result: string value

Method fromCharCode creates a new string (but not a string object) which is a concatenation Unicode characters with codes code1, code2, …, codeN.

This static method object String, so you don't need to specifically create a string object to access it. Example:

Var s = String.fromCharCode(65, 66, 67); // s equals "ABC"

indexOf method

Syntax : an object.indexOf( substring[,Start]?) Arguments: substring any string expression Start any numeric expression Result: numeric value

Method indexOf returns first position substrings in the primitive string value object. an object Start Start Start Start more than an object an object

The search is carried out from left to right. Otherwise, this method is identical to the method. The following example counts the number of occurrences of the substring pattern in the string str .

Function occur(str, pattern) ( var pos = str.indexOf(pattern); for (var count = 0; pos != -1; count++) pos = str.indexOf(pattern, pos + pattern.length); return count ; )

Italics method

Syntax : an object.italics() Result: string value

Method italics returns a string consisting of a primitive string value object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in italic font. For example, the operator document.write("My text".italics()) will display the line My text .

lastIndexOf method

Syntax : an object.lastIndexOf( substring[,Start]?) Arguments: substring any string expression Start any numeric expression Result: numeric value

Method lastIndexOf returns last position substrings in the primitive string value object an object. -1. If an optional argument is given Start, then the search is carried out starting from the position Start; if not, then from position 0, i.e. from the first character of the line. If Start negative, then it is taken equal to zero; If Start more than an object. -1, then it is taken equal an object. -1. If the object does not contain this substring, then the value -1 is returned.

The search is carried out from right to left. Otherwise, this method is identical to the method. Example:

Var n = "White whale".lastIndexOf("whale"); // n equals 6

link method

Syntax : an object.link( uri) Arguments: uri any string expression Result: string value

Method link returns a string consisting of a primitive string value object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to create a hyperlink in an HTML document with the specified uri. For example, the operator document.write("My text".link("#Bookmark")) is equivalent to the operator document.write(" My text") .

localeCompare method

Syntax : an object.localeCompare( line1) Arguments: line1 any string expression Result: number

Support

Method localeCompare compares two strings taking into account the national settings of the operating system. It returns -1 if primitive value object less lines1, +1 if it is greater lines1, and 0 if these values ​​are the same.

match method

Syntax : an object.match( Regvyr) Arguments: Regvyr Result: array of strings

Method match Regvyr object. The result of the match is an array of found substrings or null, if there are no matches. Wherein:

• If Regvyr does not contain an option global search, then the method is executed Regvyr.exec(an object) and its result is returned. The resulting array contains the found substring in the element with index 0, and the remaining elements contain substrings corresponding to the subexpressions Regvyr, enclosed in parentheses.
• If Regvyr contains a global search option, then the method Regvyr.exec(an object) is executed as long as matches are found. If n is the number of matches found, then the result is an array of n elements that contain the found substrings. Property Regvyr.lastIndex assigned a position number in the source string pointing to the first character after the last match found, or 0 if no matches were found.

It should be remembered that the method Regvyr.exec changes object properties Regvyr. Examples:

replace method

Syntax : an object.replace( Regvyr,line) an object.replace( Regvyr,function) Arguments: Regvyr — regular expression string string expression function function name or function declaration Result: new line

Method replace matches regular expression Regvyr with a primitive string value object and replaces the found substrings with other substrings. The result is a new string, which is a copy of the original string with the replacements made. The replacement method is determined by the global search option in Regvyr and the type of the second argument.

If Regvyr does not contain a global search option, then the search is performed for the first substring that matches Regvyr and it is replaced. If Regvyr contains a global search option, then all substrings matching Regvyr, and they are replaced.

line, then each found substring is replaced with it. In this case, the line may contain the following object properties RegExp, like $1 , , $9 , lastMatch , lastParen , leftContext and rightContext . For example, the operator document.write("Delicious apples, juicy apples.".replace(/apples/g, "pears")) will display the line Delicious pears, juicy pears on the browser screen.

If the second argument is function, then each substring found is replaced by calling this function. The function has the following arguments. The first argument is the found substring, followed by arguments matching all subexpressions Regvyr, enclosed in parentheses, the penultimate argument is the position of the found substring in the source string, counting from zero, and the last argument is the source string itself. The following example shows how to use the method replace you can write a function to convert Fahrenheit to Celsius. The given scenario

Function myfunc($0,$1) ( return (($1-32) * 5 / 9) + "C"; ) function f2c(x) ( var s = String(x); return s.replace(/(\d+( \.\d*)?)F\b/, myfunc); ) document.write(f2c("212F"));

will display the line 100C on the browser screen.

Please note that this method changes the properties of the object Regvyr.

Replace example

Replacing all occurrences of a substring in a string

It often happens that you need to replace all occurrences of one string with another string:

Var str = "foobarfoobar"; str=str.replace(/foo/g,"xxx"); // the result will be str = "xxxbarxxxbar";

search method

Syntax : an object.search( Regvyr) Arguments: Regvyr any regular expression Result: numeric expression

Method search matches regular expression Regvyr with a primitive string value object. The result of the match is the position of the first substring found, counting from zero, or -1 if there are no matches. At the same time, the global search option in Regvyr is ignored, and properties Regvyr do not change. Examples:

slice method

Syntax : an object.slice( Start [,end]?) Arguments: Start And end any numerical expressions Result: new line

Method slice object, from position Start to position end, without including it. If end Start and until the end of the original line.

Line character positions are numbered from zero to an object. -1. If the value Start an object. +Start. If the value end negative, then it is replaced by an object. +end. In other words, negative arguments are treated as offsets from the end of the string.

The result is a string value, not a string object. For example, the statement document.write("ABCDEF".slice(2,-1)) will print the string CDE to the browser screen.

small method

Syntax : an object.small() Result: string value

Method small returns a string consisting of a primitive string value object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text small print. For example, the statement document.write("My text".small()) will display the string My text on the browser screen.

split method

Syntax : an object.split( delimiter [,number]?) Arguments: delimiter string or regular expression number numeric expression Result: string array(object Array)

Method split breaks the primitive value object to an array of substrings and returns it. The division into substrings is done as follows. The source string is scanned from left to right looking for delimiter. Once it is found, the substring from the end of the previous delimiter (or from the beginning of the line if this is the first occurrence of the delimiter) to the beginning of the one found is added to the substring array. Thus, the separator itself does not appear in the text of the substring.

Optional argument number specifies the maximum possible size of the resulting array. If it is specified, then after selection numbers The substring method exits even if the scan of the original string is not finished.

Delimiter can be specified either as a string or as a regular expression. There are several cases that require special consideration:

IN following example regular expression is used to specify HTML tags as a separator. Operator

will display the line Text, bold, and italic on the browser screen.

strike method

Syntax : an object.strike() Result: string value

Method strike returns a string consisting of a primitive string value object, enclosed in tags …. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in a strikethrough font. For example, the statement document.write("My text".strike()) will display the string My text on the browser screen.

sub method

Syntax : an object.sub() Result: string value

Method sub returns a string consisting of a primitive string value object, enclosed in tags . There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text as a subscript. For example, the statement document.write("My text".sub()) will display the string My text on the browser screen.

substr method

Syntax : an object.substr( position [,length]?) Arguments: position And length numeric expressions Result: string value

Method substr returns a substring of the primitive value of a string object starting with this positions and containing length characters. If length is not specified, then a substring is returned starting from the given one positions and until the end of the original line. If length is negative or zero, an empty string is returned.

Line character positions are numbered from zero to an object. -1. If position greater than or equal to an object., then an empty string is returned. If position is negative, then it is interpreted as an offset from the end of the line, i.e., it is replaced by an object.+position.

Note. If position is negative, Internet Explorer mistakenly replaces it with 0, so for compatibility reasons this option should not be used.

Var src = "abcdef"; var s1 = src.substr(1, 3); // "bcd" var s2 = src.substr(1); // "bcdef" var s3 = src.substr(-1); // "f", but in MSIE: "abcdef"

substring method

Syntax : an object.substring( Start [,end]) Arguments: Start And end numeric expressions Result: string value

Method substring returns a substring of the primitive value of a string object, from position Start to position end, without including it. If end is not specified, then a substring is returned, starting from position Start and until the end of the original line.

Line character positions are numbered from zero to an object. -1. Negative arguments or equal NaN are replaced by zero; if the argument is greater than the length of the original string, then it is replaced with it. If Start more end, then they change places. If Start equals end, then an empty string is returned.

The result is a string value, not a string object. Examples:

Var src = "abcdef"; var s1 = src.substring(1, 3); // "bc" var s2 = src.substring(1, -1); // "a" var s3 = src.substring(-1, 1); // "a"

sup method

Syntax : an object.sup() Result: string value

Method sup returns a string consisting of a primitive string value object, enclosed in tags . There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text as a superscript. For example, the statement document.write("My text".sup()) will display the string My text on the browser screen.

toLocaleLowerCase Method

Syntax : an object.toLocaleLowerCase() Result: new line

Support: Internet Explorer Supported from version 5.5. Netscape Navigator Not supported.

Method toLocaleLowerCase returns a new string in which all letters of the original string are replaced with lowercase ones, taking into account the locale settings of the operating system. The remaining characters of the original string are not changed. The original string remains the same. Typically this method returns the same result as ; the difference is only possible if the language encoding conflicts with the Unicode rules for converting uppercase to lowercase letters.

toLocaleUpperCase method

Syntax : an object.toLocaleUpperCase() Result: new line

Support: Internet Explorer Supported from version 5.5. Netscape Navigator Not supported.

Method toLocaleUpperCase returns a new string in which all letters of the original string are replaced with uppercase, taking into account the locale settings of the operating system. The remaining characters of the original string are not changed. The original string remains the same. Typically this method returns the same result as ; the difference is only possible if the language encoding conflicts with the Unicode rules for converting lowercase letters to uppercase letters.

toLowerCase method

Syntax : an object.toLowerCase() Result: new line

Method toLowerCase returns a new string with all letters of the original string replaced with lowercase ones. The remaining characters of the original string are not changed. The original string remains the same. For example, the statement document.write("String object".toLowerCase()) will display the string string object.