How to print log in javascript

Printing logs in JavaScript is a very important function, and it is often used whether during development or debugging. JavaScript is a dynamically typed, interpreted language. Its code is interpreted and executed at runtime. There is no compilation process like static compiled languages ​​such as Java and C. Therefore, we need to rely on printing logs to view program execution.

This article will introduce how to print logs in JavaScript, including the use of console.log() method, call stack dump, use of debugging tools, etc.

1. Console.log() method

console.log() is JavaScript’s built-in method for outputting the console. It can output one or more values ​​on the console and is widely used. for debugging and troubleshooting.

Its basic syntax is as follows:

console.log(object1 [, object2, ..., objectN]);

Among them, object1 to objectN are a set of data objects to be output, which can be multiple parameters or an array.

If the output is a string, you can use a template string to output it. For example:

console.log(`Hello, ${name}!`);

The output effect in the console is as follows:

Hello, Bob!

2. Call stack dump

Sometimes we need to view the call stack information of the current code execution. In order to have a deeper understanding of the order and flow of code execution.

In JavaScript, console.trace() can be used to print call stack information. Its basic syntax is as follows:

console.trace();

It will output the current call stack information, including the functions called by the code , files and other information. As shown below:

function three() {
    console.trace();
}

function two() {
    three();
}

function one() {
    two();
}

one();

The output effect in the console is as follows:

three @ index.html:5
two @ index.html:9
one @ index.html:13
(anonymous) @ index.html:16

We can see that the call stack of the current code is:

one() -> two() -> three()

3. Debugging Tools Using

In JavaScript, in addition to console.log() and console.trace(), you can also use debugging tools to help us debug the code.

Modern browsers have built-in developer tools that allow us to debug JavaScript code more conveniently. We can help us find problems in the code by using breakpoints, viewing variable values, single-step debugging and other tools.

The developer tools provided by Chrome browser are one of the most popular debugging tools at present. It provides a very rich debugging tools, as shown in the following figure:

Through the developer tools, we can view the context information of the current code execution, view variable values, view call stack information, set breakpoints, etc. These tools are very useful in the code debugging process and can improve our debugging efficiency.

4. Summary

Printing logs in JavaScript is a very important function. It can help us understand the flow and process of code execution, and plays a key role in debugging and error troubleshooting. . This article introduces the method of printing logs in JavaScript, including the use of console.log() method, call stack dump, use of debugging tools, etc. I hope this article can help readers better grasp the logging function of JavaScript and improve the efficiency of code debugging.

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