How to use JS to merge arrays and objects-JS Tutorial-php.cn

This time I will show you how to use JS to merge arrays andobjects. What are theprecautionsfor using JS to merge arrays and objects. The following is a practical case. Let’s take a look.

1 Array merging

1.1 concat method

var a=[1,2,3],b=[4,5,6]; var c=a.concat(b); console.log(c);// 1,2,3,4,5,6 console.log(a);// 1,2,3 不改变本身

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1.2 Loop traversal

var arr1=['a','b']; var arr2=['c','d','e']; for(var i=0;i
        
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1.3 apply

To merge array arr1 and array arr2, use Array.prototype.push.apply(arr1, arr2) or arr1.push.apply( arr1,arr2);

var arr1=['a','b']; var arr2=['c','d','e']; Array.prototype.push.apply(arr1,arr2); //或者 arr1.push.apply(arr1,arr2);
console.log(arr1) //['a','b','c','d','e']

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2 Object merge

2.1 $.extend()

var obj1= {'a': 1}; var obj2= {'b': 1}; var c = $.extend(obj1, obj2); console.log(obj1); // {a: 1, b: 1} obj1已被修改 //或者 
var obj3 = $.extend({}, obj1, obj2) 
console.log(obj3); //{a: 1, b: 1} 不会改变obj1,obj2

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2.2 Traversal assignment

var obj1={'a':1}; var obj2={'b':2,'c':3}; for(var key in obj2){ if(obj2.hasOwnProperty(key)===true){ 
 //此处hasOwnProperty是判断自有属性， 使用 for in 循环遍历对象的属性时，原型链上的所有属性都将被访问会避免原型对象扩展带来的干扰 obj1[key]=obj2[key]; } } console.log(obj1);//{'a':1,'b':2,'c':3};

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2.3 Obj.assign()

You can copy any number of the source object’s own enumerable properties to the target object, and then Return the target object.

Object.assign(target, ...sources) //a. 复制一个对象
var obj = { a: 1 ,b:2}; var copyObj = Object.assign({}, obj); console.log(copyObj); // { a: 1,b:2 }

//b.合并多个对象 var o1 = { a: 1 }; var o2 = { b: 2 }; var o3 = { c: 3 }; var obj = Object.assign(o1, o2, o3); console.log(obj); // { a: 1, b: 2, c: 3 } console.log(o1); // { a: 1, b: 2, c: 3 }, 且目标对象自身也会改变。

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2.4 Deep copy and shallow copy of object

2.4.1 Shallow copy

var obj1={'a':1}; var obj2={'b':{'b1':22,'b2':33}}; $.extend(obj1, obj2); //obj1拷贝了obj2的属性 console.log(obj1) // {'a':1,'b'{'b1':22,'b2':33}} console.log(obj1.b.b1) // 22 obj2.b.b1=44; //obj2重新赋值 console.log(obj1.b.b1) // 44 obj1.b仅拷贝了对象的指引，所以受原obj2的影响

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2.4.2 Deep copy

var obj1={'a':1}; var obj2={'b':{'b1':22,'b2':33}}; $.extend(true,obj1, obj2); //第一个参数设为true表示深复制 console.log(obj1) // {'a':1,'b'{'b1':22,'b2':33}} console.log(obj1.b.b1) // 22 obj2.b.b1=44; //obj2重新赋值 console.log(obj1.b.b1) // 22 obj1拷贝了obj2的所有属性以及值，并不受obj2的影响

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I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!