JavaScript Array Detailed Summary

1. Array Induction

1. Split a string into an array
2. Convert collections and maps to new arrays
3. Make a shallow copy of an existing array
4. The arguments object can be easily converted to an array
5. Convert custom objects

2. Iterator Method

3. Common array operations

1. Array Induction

1. Split a string into an array

 console.log(Array.form("red")) // ["r", "e", "d"]

2. Convert collections and maps to new arrays

 const a1 = new Map().set("name","张三").set("age",18)

    console.log(Array.from(a1)) // [["name","张三"], ["age",18]

3. Make a shallow copy of an existing array

 const a1 = [

        {

        name: "Xiao Ming",

        age: 18,

        gender: "male"

        },

        {

            name: "Xiao Ming",

            age: 18,

            gender: "male"

        }]

    const a2 = Array.from(a1)

    console.log(a2)

Running results:

4. The arguments object can be easily converted to an array

 function argumentArray() {

        console.log(Array.from(arguments)) // [1, 2, 3, 4]

    }

    argumentArray(1, 2, 3, 4)

5. Convert custom objects

let arrayLike = {

        0: 'Zhang San',

        1: '18',

        2: 'Male',

        3: ['Guess', 'Which one'],

        'length': 4

    }

    let arr = Array.from(arrayLike);

    console.log(arr);

Running results:

Array.of(參數) will convert the parameter to an array

 Array.of(1, 2, 3, 4) // [1, 2, 3, 4]

2. Iterator Method

There are three methods on the Array prototype for retrieving arrays: keys() , values() , entries()

 Array.of(1, 2, 3, 4) // [1, 2, 3, 4] 


 let user = [

        {

            name: "Zhang San",

            age: 18,

            gender: "male"

        },

        {

            name: "Li Si",

            age: 19,

            gender: "female"

        },

        {

            name: "Wang Wu",

            age: 20,

            gender: "female"

        }

    ]

First use user.key()， to traverse the returned array index

 console.log(Array.from(user.keys())) // [0, 1, 2]

user.values()， traverse and return array elements

 console.log(Array.from(user.values()))

user.entries()， traverse and return index/value pairs

console.log(Array.from(user.entries()))

3. Common array operations

slice(stratIndex，endIndex)

If the parameters are full, return all elements from the start index to the end index;
If there is only one parameter, return the corresponding elements from the start index to the end index.

splice(startIndex, length, new1, new2....)

To delete, replace or insert

 let newData = {"username": "ys","age": "22","gender":"Ji Ke 1902","className":"Class 3","id":6}

    person.splice(1,1,newData) // This is where the replacement is used

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