How to open javascript console in Yandex browser. Convenient Chrome Developer Console Features You May Not Know About

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Using the console in the browser, the user views the errors that occur when loading pages. He can work with this page, which includes the execution of various command actions on it.

With the help of such a "tool" in the browser, you can get rid of failures in the work of scripts on a web page in time. This saves a lot of time for the user.

To be able to use the browser tool, the first thing to do is launch it. How do you open the console in Opera?

Types of errors

Now web programmers do not have to puzzle over what kind of problem arose in the browser. With the help of the "tool" you can display all the information about it.

When you open the console, a window will appear where the page analysis will be displayed. The window that opens has five tabs: JS, HTTP, CSS, About, DOM.

Instructions

Sequencing:

Open the Opera browser and go to the Menu located in the upper left corner of the screen.
We are looking for the "Tools" section, click on it.
Select "Advanced", open "Console".

After completing these steps, a window will appear in the browser, which will open all the errors that have ever occurred when launching sites.

There is also a faster way to cause errors in the Opera. Press the key combination "Ctrl + Shift + I". A window will open where you should click on the "Console" section.

Modern browsers provide built-in development tools for JavaScript and other technologies. These tools include a console, which is similar to a shell interface, as well as tools for DOM inspection, debugging, and network activity analysis.

The console can be used to log information as part of the JavaScript development process. The console also allows you to interact with the web page by executing JavaScript expressions in the context of the page. Basically, the console provides the ability to write JavaScript code and manipulate it as needed.

This guide will teach you how to use the JavaScript console in your browser and introduce you to other built-in development tools that you might find useful.

Working with the JavaScript console in the browser

Most modern web browsers that support HTML and XHTML provide by default access to the developer console, where you can work with JavaScript in a terminal shell-like interface. In this section, you will learn how to access the console in Firefox and Chrome.

Firefox browser

These tools allow you to inspect and edit DOM elements, as well as search for HTML objects associated with a specific page. The DOM can indicate whether a piece of text or an image has an ID attribute, and can determine the value of that attribute.

Additionally, in the sidebar or below the DOM panel, you can find CSS styles that are used in an HTML document or style sheet.

To edit the DOM in real time, double-click on the selected element. For example, you can try turning the tag

v

.

Again, after the refresh, the page will return to its previous appearance.

Network tab

The Network tab allows you to monitor and record network requests. This tab shows the browser's network requests, including requests to load the page, the time it takes to serve the requests, and information about each of them. This data can be used to optimize page load performance and debug queries.

You can use the Network tab in conjunction with the JavaScript Console. For example, you can start debugging a page using the console and then open the Network tab and view network activity without reloading the page.

Responsive design

Responsive websites quickly adapt their look and feel across a variety of devices: mobile phones, tablets, desktops, and laptops. Screen size, pixel density, and touch response are factors to consider when designing responsive websites. Also, the principles of responsive design are important to consider in order for the website to be accessible and efficient, regardless of the device on which it is opened.

Modern browsers (including Firefox and Chrome) provide models for adhering to responsive design principles when developing websites and applications. These models emulate the behavior of a particular device, which allows you to test and analyze all the functions of the site.

You can read more about this in the browser guides:

Responsive Design Mode in Firefox

Conclusion

This tutorial provides a quick overview of working with the JavaScript console in modern web browsers. You can also find information on other useful development tools here.

The browser from the well-known Russian corporation Yandex appears to be one of the most popular browsers on the Russian-speaking Internet. It owes its popularity to advanced functionality and an abundance of hidden features, many of which are used by professionals in the process.

These tools include the console, which is very often used to find and fix errors in the browser, as well as to perform a number of other tasks.

Console Features

Before figuring out how to open the console in a Yandex browser, you should decide what it is and what such a tool can be used for. As you know, the Yandex browser was developed on the basis of two other already existing projects, namely Chrome, which allowed its developers to implement a number of developments in their own browser. It was in these programs that the console appeared, which can be used to solve a wide range of tasks.

These include:

Development of web pages;
View the codes of the loaded sites;
Checking the performance of scripts;
Identification of errors and malfunctions of sites.

IMPORTANT! Taking into account the importance of such tasks, we can confidently call the console one of the main tools for a web developer.

In this regard, it is extremely important to learn how to open such a tool using the capabilities of the browser. However, it should be borne in mind that an unprepared user who does not have the appropriate skills to work with such kind of tools should be careful not to disrupt the browser's performance.

How to open?

You can open the console in this browser in two ways at once. The first one is graphical, involving the use of the main browser menu, while the second one involves the use of hot keys. For beginners, the first seems to be the most suitable.

ADVICE! They can be difficult for novice users to remember, but using them allows you to access the right tool much faster.

There are several consoles in this browser, and each one serves to solve specific problems. To access them using the graphical method, you need to press a special button that looks like three horizontal stripes, and then select the Additional section. In it, you should go to the Additional Tools category, after which you will need to select the desired console.

Hotkeys

In order to save time, it is very convenient to use hotkeys while the browser is running, as they allow you to move much faster to the desired item or menu. The same applies to consoles, each of which has its own individual shortcut keys for invoking.

So, in order to examine the source code of the currently viewed page, you need to press Ctrl + U, which will immediately open this tool. To access the developer tools, you need to press three keys at once: Ctrl + Shift + I. Its capabilities, as a rule, are not of interest to the average user who is not involved in the development of web pages or applications.

The console is perhaps the most important, as it is responsible for the functioning of various scripted elements on the page. Any advertising, interactive applications and other types of content are scripted, and therefore, the capabilities of this console can hardly be overestimated. To access it, press Ctrl + Shift + J, which will allow you to view the codes that were used on the page.

Video to help

The Chrome DevTools command line API contains many convenient functions for performing simple tasks: selecting and inspecting DOM elements, displaying data in a readable format, running and validating a profiler, and monitoring DOM events.

Note: this API is only available inside the console. You cannot access the API command line from scripts on the page.

$_

$ _ returns the value of the last executed expression.

The example below executes a simple expression (2 + 2). Then $ _ is executed, which is assigned the same value:

In this example, the executed expression contained an array of names. Executing $ _. Length will give the length of the array, and the $ _ expression itself will take the value of the last expression executed, which is 4:

$0 – $4

The $ 0, $ 1, $ 2, $ 3 and $ 4 commands work as links to the last 5 DOM elements that were viewed in the Elements panel, or to the last 5 JS heap objects that were selected in the Profiles panel. $ 0 returns the last selected item or object, $ 1 returns the one before it, and so on.

In the example below, an element of the medium class is selected in the Elements panel. In the console, $ 0 took on the same meaning:

In the image below, another item is selected on the same page. $ 0 now refers to this item and $ 1 to the previous one:

$ (selector)

$ (selector) returns a reference to the first DOM element with the specified CSS selector. This function is shorthand for the document.querySelector () function.

Right click on the result and select "Reveal in Elements Panel" to find an element in the DOM or "Scroll in to View" to see it on the page.

Note: If you are using libraries like jQuery that use the $ symbol, then the functionality of that library will be used.

$$ (selector)

$$ (selector) returns an array of elements containing the specified selector. This command is equivalent to calling document.querySelectorAll ().

The following example uses $$ () to create an array of all elements in the document and returns the src property of each element:

Var images = $$ ("img"); for (each in images) (console.log (images.src);)

Note: Press Shift + Enter in the console to go to a new line without executing the script.

$ x (path)

$ x (path) returns an array of elements that match the given XPath expression.

This example will return all elements

$ x ("// p")

And this one is all the elements

Containing element :

$ x ("// p [a]")

Note: Profilers can run concurrently and do not need to be closed in order of creation.

table (data,)

Output of object data in table format. For example, to display a list of names, do the following:

Var names = (0: (firstName: "John", lastName: "Smith"), 1: (firstName: "Jane", lastName: "Doe")); table (names);

undebug (function)

undebug (function) stops debugging the specified function.

Undebug (getData);

unmonitor (function)

unmonitor (function) stops monitoring the specified function.

Unmonitor (getData);

unmonitorEvents (object,)

unmonitorEvents (object,) stops monitoring the specified object and events:

UnmonitorEvents (window);

You can also stop monitoring individual events:

MonitorEvents ($ 0, "mouse"); unmonitorEvents ($ 0, "mousemove");

values (object)

values (object) returns an array containing the values of all properties of the specified object.

Translation

How can I use the developer console to turn Google Chrome into something like a text editor? What is the point in it acquires the icon familiar to many from jQuery $ ? How to display a set of values in the form of a decent table to the console? If the answers to these questions do not come to mind right away, then the tab Console from the Chrome developer tools has not yet revealed itself in all its glory.

At first glance, we have before us a completely ordinary JavaScript console, which is suitable only for displaying server response logs or variable values into it. By the way, I used it like that when I just started programming. However, over time, I gained experience, learned a little, and unexpectedly discovered that the Chrome console can do a lot of things that I never knew. I want to tell you about it today. Yes, if you are not reading now on a mobile phone, you can immediately try it all.

1. Selecting DOM elements

If you are familiar with jQuery, it’s not for me to tell you about the importance of constructs like $ (‘. Class’) and $ (‘Id’)... For those who are not in the know, I will explain that they allow you to select DOM elements by specifying the classes and IDs assigned to them. The developer console has similar functionality. Here, "$", however, has nothing to do with jQuery, although it does essentially the same thing. This is an alias for the function document.querySelector ().

View commands $ (‘TagName’), $ (‘. Class’), $ (‘# Id’) and $ (‘. Class #id’) return the first DOM element that matches the selector. At the same time, if jQuery is available in the document, its "$" will override this console functionality.

There is one more construction here: $$ ... Its use looks like $$ (‘tagName’) or $$ (‘. Class’)... It allows you to select all the DOM elements that match the selector and place them in an array. Working with it is no different from other arrays. In order to select a specific item, you can refer to it by index.

For example, the command $$ (‘. ClassName’) will provide us with an array of all page elements with the specified class name when calling it. Commands $$ (‘. ClassName’) and $$ (‘. ClassName’) will give access, respectively, to the first and second element of the resulting array.

Experimenting with commands $ and $$

2. Turning the browser into a text editor

Have you ever caught yourself thinking that it would be nice to edit the text of the debugged web page right in the browser? If yes, then you will like the command shown below.

Document.body.contentEditable = true
After its execution in the console, the document opened in the browser can be edited without having to search for the desired fragment in the HTML code.

3. Finding event handlers attached to an element

As you debug, you may need to find event handlers attached to elements. It is very easy to do this using the console. It is enough to use the following command:

GetEventListeners ($ (‘selector’))
As a result of its execution, an array of objects will be issued containing a list of events to which the element can react.

Event handlers

In order to find a handler for a specific event, you can use the following construction:

GetEventListeners ($ (‘selector’)). EventName.listener
This command will display the code of the event handler function. Here eventName Is an array that contains all events of a particular type. For example, in practice it might look like this:

GetEventListeners ($ (‘# firstName’)). Click.listener
As a result, we get the code of the function associated with the event click element with id firstName.

4. Event monitoring

If you want to observe the occurrence of events tied to a specific DOM element, the console can help you with that. Here are some commands that you can use to monitor events.

Command monitorEvents ($ (‘selector’)) allows you to monitor all events associated with the element that the selector matches. When an event occurs, an entry is made in the console. For example, the command monitorEvents ($ (‘# firstName’)) will allow logging all events associated with an element whose identifier is - firstName.
Command monitorEvents ($ (‘selector’), ’eventName’) similar to the previous one, but it targets a specific event. Here, in addition to the element selector, the event name is also passed to the function. Such a command will display data on the occurrence of one event to the console. For example, the command monitorEvents ($ (‘# firstName’), ’click’) will display information only by event click element with id firstName.
Command monitorEvents ($ (‘selector’), [‘eventName1’, ’eventName3”,….]) allows you to monitor several selected events. Here, a string array is passed to the function, which contains the names of the events. For example, a command like this: monitorEvents ($ (‘# firstName’), [‘click’, ’focus’]) will output information about events to the console click and focus for element with id firstName.
Command unmonitorEvents ($ (‘selector’)) allows you to stop monitoring and logging events in the console.

5. Measuring the execution time of a piece of code

A function of the form is available in the Chrome console console.time (‘labelName’) which takes a label as an argument and starts a timer. Another function, console.timeEnd (‘labelName’), stops the timer to which the label passed to it is assigned. Here's an example using these functions:

Console.time ("myTime"); // Starts a timer labeled myTime console.timeEnd ("myTime"); // Stops the timer labeled myTime // Output: myTime: 123.00 ms
The above example lets you know the time between starting and stopping the timer. You can do the same inside a JavaScript program and find the execution time of a piece of code.

Let's say I need to figure out the duration of a loop. You can do it like this:

Console.time ("myTime"); // Starts a timer labeled myTime for (var i = 0; i< 100000; i++){ 2+4+5; } console.timeEnd("mytime"); // Останавливает таймер с меткой myTime //Вывод - myTime:12345.00 ms

6. Displaying the values of variables in the form of tables

Suppose we have an array of objects like this:

Var myArray = [(a: 1, b: 2, c: 3), (a: 1, b: 2, c: 3, d: 4), (k: 11, f: 22), (a: 1 , b: 2, c: 3)]
If you display it in the console, you get a hierarchical structure in the form of, in fact, an array of objects. This is a useful feature, branches of the structure can be expanded by viewing the contents of objects. However, with this approach, it is difficult to understand, for example, how the properties of similar elements are related. In order to make it more convenient to work with such data, they can be converted to a tabular form. To do this, use the following command:

Console.table (variableName)
It allows you to display a variable and all its properties in the form of a table. This is how it looks.

Displaying an array of objects as a table

7. View item code

You can quickly jump to the item code from the console using the following commands:

Command inspect ($ (‘selector’)) allows you to open the code of the element corresponding to the selector in the panel Elements Google Chrome developer tools. For example, the command inspect ($ (‘# firstName’)) will allow you to view the code of the element with the id firstName... Command inspect ($$ (‘a’)) will open the code for the fourth link that is present in the DOM.
View commands $0 , $1 , $2 allow you to quickly jump to recently viewed items. For example, $0 will open the code for the most recently viewed item, and so on.

8. Listing of element properties

If you need to view a list of element properties, the console will help you with that as well. Here's a command like this:

Dir ($ (‘selector’))
It returns an object containing properties associated with the specified DOM element. As with other similar cases, the contents of this object can be explored by viewing its tree structure.

9. Calling the last received result

The console can be used as a calculator, as everyone probably knows. But the fact that it has built-in tools that allow you to use the results of previous calculations in commands is known to few. By construct $_ you can retrieve the result of the previous expression from memory. This is how it looks:

2 + 3 + 4 9 // - Summation result - 9 $ _ 9 // The last received result is displayed $ _ * $ _ 81 // Since the last result is 9, we get 81 Math.sqrt ($ _) 9 // Square root from the last result, which was $ 81 _ 9 // Again we get 9 - the result of the previous calculation

10. Clearing Console and Memory

If you need to clear the console and memory, use this simple command:

Clear ()
After pressing Enter, the blank console will be ready for new experiments.
That's all.

11, 12, 13, 14…

Frankly speaking, this is not all. I've shown just some of the non-obvious features of the Google Chrome console. In fact, their