You don’t know console, makes JS debugging easier

For engineers at the front end, console is no stranger to you, but how much can you know? Today let xiaopeng take a look at the world before big.

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! ');
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2. Console.dir () displays an object for all properties and methods

console.dir(document);
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3. Console.table () displays the data as a table

This method takes a required parameter, data, which must be either an array or an object

var names = [
    {
        name: "Xiao Ming",
        age: 20,
        gender: 'male'
    },
    {
        name: "Little red",
        age: 18,
        gender: 'woman'
    },
    {
        name: "Xiao li",
        age: 22,
        gender: 'male'
    }
]

console.table(names)
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4. Calculate the time occupied by the 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');
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5. Output the number of calls

Console.count () This function takes an optional argument label

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

user = 'Bob'; // Lable is Bob Greate (); user ='John'; // Lable is John Greate (); greate(); console.count('John');
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6. Determine whether the assertion is true

Console.assert () writes an error message to the console if the assertion is false, or true if the assertion is true. There is no response

console.assert(1==1, 'Success');
console.assert(1==2, 'Error');
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Group 7.

Console.group () creates a group on the console until the group ends with a call to console.groupend ()

console.group('Today's Event');
    console.log('eat');
    console.log('sleep');
    console.log('Beat the beans');
console.groupEnd();

console.group('Things for Tomorrow');
    console.log('hanami');
    console.log('moon');
    console.log('Autumn fragrance');
console.groupEnd();
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