Summary of ES6 commonly used array methods

1、Array.from()

Used for array-like objects (that is length, objects with attributes) and traversable objects into real arrays.

let json ={
    
    
	    '0':'11',
	    '1':'22',
	    '2':'33',
	    length:3
	}
	let arr = Array.from(json);
	console.log(arr); // ["11", "22", "33"]	

2、Array.of()

Convert a set of values ​​into an array, the parameters are not divided into types, only the number, and the number is 0 to return an empty array.

let arr1 = Array.of(1,2,3);	
	let arr2 = Array.of([1,2,3]);
	let arr3 = Array.of(undefined);
	let arr4 = Array.of();
	console.log(arr1); // [1, 2, 3]
	console.log(arr2); // [[1, 2, 3]]
	console.log(arr3); // [undefined]
	console.log(arr4); // []

3、find()

find()The method returns the value of the first element in the array that satisfies the provided test function. Otherwise, it returns undefined. The parameter is the callback function.

let arr=[12,32,43,2,4,11,55,12];
let val=arr.find(function (ele,index) {
    
    
   return ele>12;
});
 console.log(val);//11

4、findIndex ()

findIndexIt's findalmost the same, but the index is returned by default. If there is no eligible element, it returns -1

let arr=[12,32,43,2,4,11,55,12];
let val=arr.findIndex(function (ele,index) {
    
    
    return ele>32;
});
console.log(val);

5、fill()

fill()Method is used to replace an element of the array with a fixed value.

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.fill("Runoob");//Runoob,Runoob,Runoob,Runoob

6. Traverse the array method keys(), values(), entries()

These three methods all return a traverser object, which can be for...oftraversed in a loop. The only difference keys()is the traversal of the key name, the traversal of values()the key value, and the traversal entries()of the key-value pair.

keys()

	let arr = ["a","b","c","d"];
	for(let i of arr.keys()){
    
    
		console.log(i);
	}
    //打印：
    // 0
    // 1
    // 2
    // 3

values()

	let arr = ["a","b","c","d"];
	for(let i of arr.values()){
    
    
		console.log(i);
	}
    //打印：
    // a
    // b
    // c

entries()

 let arr = ["a","b","c","d"];
    for(let i of arr.entries()){
    
    
        console.log(i);
    }
    //打印：
    // [0, "a"]
    // [1, "b"]
    // [2, "c"]
    // [3, "d"]
    for(let [idx,item] of arr.entries()){
    
    
        console.log(idx+":"+item);
    }
    //打印：
    // 0:a
    // 1:b
    // 2:c

7、includes()

includes()The method is used to determine whether an array contains a specified value, if it is returned true, otherwise false.

[1, 2, 3].includes(2);     // true
[1, 2, 3].includes(4);     // false
[1, 2, 3].includes(3, 3);  // false
[1, 2, 3].includes(3, -1); // true
[1, 2, NaN].includes(NaN); // true

8、copyWithin()

copyWithin()The method is used to copy elements from a specified position in the array to another specified position in the array. Will overwrite the original members.

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.copyWithin(2, 0);//Banana,Orange,Banana,Orange