How to implement console output in js

In js, you can use the Console object to achieve console output. Commonly used console output commands are: console.log(), console.info(), console.error(), console .warn() etc.

#This article will introduce to you what the Console object is? What is the use? Let everyone know about common console output commands. The following is a specific introduction, I hope it will be helpful to you. [Recommended related video tutorials: JavaScript Tutorial]

Console object

The Console object is a built-in provided by the browser Object is used for JavaScript debugging and access to the debugging console. There is no Console object in native JS by default.

Common uses:

1. When an error occurs when the web page code is running, the running error message is displayed.

2. Provides a command line interface for interacting with web page code.

How to open the console:

1. Open the audit panel through the F12 key, select the console panel in the audit panel,

2. Click Right-click the mouse, select the Inspect Element (Inspection) tab, select console panel

3 in the audit panel, Google Chrome, press ctrl shift I, open the console panel.

Console output commands

Let’s take a look at the commonly used console output commands:

1 , console.log(): Output a message on the console.

Syntax:

console.log(object[, object, ...]);

Note: When there are multiple parameters, they need to be separated by spaces.

console.log() supports printf’s placeholder format output. Supported placeholders are: characters (%s), integers (%d or %i), floating point numbers (%f) and objects (%o):

Example:

console.log("%d年%d月%d日",2018,12,10);

Output:

##2. console.info(): Output a message on the console.

console.info() is an alias of console.log(), and its effect is similar to console.log().

Example:

console.info(“消息”);
console.info("%d年%d月%d日",2018,12,10);

3. console.error(): Output a message representing the error

When outputting information, a red cross will be added at the front to indicate an error, and the stack where the error occurred will be displayed.

Example:

##4, console.warn():

Output warning informationWhen outputting information , a yellow triangle with an exclamation mark will be added at the front to indicate a warning.

Example:

##5. console.assert()

: Judgment output

Syntax:

console.assert(表达式,字符串)

Only when the result of the expression is false, the string will be output, that is, an exception will be thrown; otherwise, there will be no output result.

Example:

var year = 2014;
console.assert(year == 2018,"错误" );

Rendering:

##6, console.table(): Convert composite type data to table output and display

Example:

var arr= [ 
         { num: "1"},
         { num: "2"}, 
         { num: "3" }
    ];
console.table(arr);
var obj= {
     a:{ num: "1"},
     b:{ num: "2"},
     c:{ num: "3" }
     };
console.table(obj);

Rendering:

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