The console you don't know makes JS debugging easier

For the front-end engineers, you will definitely not be unfamiliar with the console, but how much do you know? Let Xiaopeng take a look at the big former world today.

Chrome Console - Developer Tools

Windows press F12, MAC press Command + Option + C or Command + Option + J to open the console

1. Output a message to the web console

 console.log('Hello world!');
console.info('Hello world!');
console.warn('Hello world!');
console.error('Hello world!');
console.debug('Hello world!');

2. console.dir() displays an object for all properties and methods

 console.dir(document);

3. console.table() displays the data in the form of a table

This method requires a mandatory parameter data, which must be an array or an object

 var names = [
    {
        name: "小明",
        age: 20,
        gender: '男'
    },
    {
        name: "小红",
        age: 18,
        gender: '女'
    },
    {
        name: "小李",
        age: 22,
        gender: '男'
    }
]

console.table(names)

4. The time taken by the calculation operation

Note: Each timer must have a unique name

 console.time('timer');
let count = 0;
for (let i=0; i<100; i++) {
    count++;
}
console.timeEnd('timer');

5. Output the number of times it was called

console.count() This function accepts an optional parameter label

 let user = "";
function greate () {
    console.count(user);
    return 'hi' + user;
}

user = 'Bob';
// 此时的lable是Bob
greate();

user = 'John';
// 此时的lable是John
greate();
greate();
console.count('John');

6. Determine if an assertion is true

console.assert() Writes an error message to the console if the assertion is false, if the assertion is true. nothing happens

 console.assert(1==1, 'Success');
console.assert(1==2, 'Error');

7. Grouping

console.group() creates a group on the console until the group ends after calling console.groupEnd()

 console.group('今日事项');
    console.log('吃饭');
    console.log('睡觉');
    console.log('打豆豆');
console.groupEnd();

console.group('明日事项');
    console.log('赏花');
    console.log('赏月');
    console.log('赏秋香');
console.groupEnd();