How to debug breakpoints in JavaScript

When doing complex JavaScript development, debugging the code is essential. An important tool for JavaScript debugging is breakpoints. A breakpoint means that when the code is executed to a certain position, the program will pause execution so that we can analyze and debug the code. In this article, we will learn how to set breakpoints in JavaScript.

Set breakpoints in the Chrome browser

The Chrome browser has a powerful built-in development tool that can help us debug JavaScript code. In the Chrome browser, we can set breakpoints through the following steps:

1. Open the developer tools

In the Chrome browser, we can use the menu bar or shortcut keys Open developer tools. Specifically, select "Menu Bar -> More Tools -> Developer Tools" or use the shortcut key F12. After opening the developer tools, select the "Sources" tab.

2. Find the JavaScript file you want to debug

In the "Sources" tab, you can find the JavaScript file being loaded. If there are many files, you can use the search box to find them quickly. Alternatively, you can find JavaScript files through the network panel.

3. Set a breakpoint on a line of code

After you find the JavaScript file you want to debug, you can set a breakpoint on a line of code. Click the empty space to the left of the code line number and Chrome will set a red dot at that location to indicate that it is a breakpoint.

4. Start code execution and wait for the program to pause

After setting the breakpoint, you can refresh the page and reload the JavaScript file. When the code execution reaches the breakpoint position, the program will pause execution and the page will stop at the debugging interface under the "Sources" tab. At this point you can use debugging tools to analyze the code and view the values ​​of variables.

Set breakpoints in VS Code

VS Code is a popular text editor that also has good support for JavaScript development. In VS Code, we can also set breakpoints to debug JavaScript code.

1. Open JavaScript file

After opening the JavaScript file to be debugged, click in the blank area to the left of the code line, and a breakpoint will be set at that location. At this time, a red circle will appear on the left side of the line, indicating that this position is a breakpoint.

2. Start code execution and wait for the program to pause

In VS Code, you also need to start code execution to trigger a breakpoint pause. Click the "Debug" tab and then click the "Start Debugging" button. VS Code opens the debugger panel and starts program execution. When the program execution reaches the breakpoint location, the program will pause execution and display debugging information in the debugger panel.

Use the Console.log statement to debug code in the browser

In addition to the methods introduced above, we can also use the Console.log statement to debug JavaScript code. The Console.log statement can output information to the console so that we can observe the execution of the program. After adding the Console.log statement to the code, information will be printed on the console when the code is executed.

Summary

In JavaScript development, debugging is an essential process. Breakpoints are an important tool in JavaScript debugging, which can help us analyze the code execution flow and view the values ​​of variables. In both Chrome browser and VS Code, JavaScript debugging can be achieved by setting breakpoints. In addition to breakpoints, we can also use the Console.log statement to output debugging information. Proficiency in debugging tools and methods can improve the efficiency and quality of JavaScript development.

The above is the detailed content of How to debug breakpoints in JavaScript. For more information, please follow other related articles on the PHP Chinese website!