How to convert object to array in javascript

Methods for converting JavaScript objects into arrays: 1. Through the "[].slice.call(object)" statement; 2. Using the "Array.from(object)" statement, "Array.from()" Methods can convert traversable objects into arrays (including Set and Map data structures).

The operating environment of this tutorial: Windows 7 system, JavaScript version 1.8.5, Dell G3 computer.

1. Convert an array-like object into an array

1. What is an array-like object

For example:

let arrayLike = {
    '0':"z",
    '1':"y",
    '2':"k",
    length:3
};

The essence is that it has the length attribute, which can be obtained in a similar way to obtaining elements of an arrayarrayLike[0], arrayLike[1] element, you can also get the length of the pseudo array through arrayLike.length.

Common pseudo-arrays include the NodeList collection obtained through DOM operations (document.querySelectorAll('p')), and function formal parameters arguments.

2. Conversion method

Method 1: Through [].slice.call(arrayLike)

//获取当前dom的span组成的伪数组
let spanDomArr = document.querySelectorAll('span');
 
//通过数组的方法forEach遍历spanDomArr
let arr = [].slice.call(spanDomArr);
 
//因为spanDomArr是伪数组，不支持数组的forEach，所以需要先转换成数组
arr.forEach(function(span){
    console.log(span)
});

Method 2: Through Array.from(arrayLike)

//获取当前dom的span组成的伪数组
let spanDomArr = document.querySelectorAll('span');
 
//通过数组的方法forEach遍历spanDomArr
//因为spanDomArr是伪数组，不支持数组的forEach，所以需要先转换成数组
Array.from(spanDomArr).forEach(function(span){
    console.log(span)
});

2. Extend-Array.from( )

1. Function:

1-Can convert array-like objects into arrays;

2-Can convert traversable Convert the object into an array (including ES6's new data structures Set and Map);

2. Practical application:

1-If the current browser does not deploy this method, you can use the Array.prototype.slice method instead

/*
 *  方法名：objectToArray
 *  功能介绍：把类似数组的对象、可遍历的对象转换成数组
 *  参数：obj-需要转换的对象
 */
var objectToArray = function(obj){
   return Array.from ? Array.from(obj) : [].slice.call(obj);
};

2-If the parameter is an array, an identical array will be returned

Array.from(["z","y","k"]);
//打印：["z","y","k"]

3-Objects with only length attributes cannot be passed array.from conversion

4-Array.from second parameter: is used to process each element and put the processed value Return into array.

let arrayLike = {
    "0" : "z",
    "1" : "y",
    "2" : "k",
    "length":3
};
Array.from(arrayLike,x=>x+'1');
//等同于
Array.from(arrayLike).map(x=>x+'1');

//打印：["z1","y1","k1"]

【Related recommendations: javascript learning tutorial】

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