How to use JS to merge arrays and objects

This time I will show you how to use JS to merge arrays and objects. What are the precautions for 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

1.2 Loop traversal

var arr1=['a','b'];
var arr2=['c','d','e'];
for(var i=0;i<arr2.length;i++){
   arr1.push(arr2[i]) 
}
console.log(arr1);//[&#39;a&#39;,&#39;b&#39;,&#39;c&#39;,&#39;d&#39;,&#39;e&#39;]

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);<br>console.log(arr1) //['a','b','c','d','e']

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 <br>var obj3 = $.extend({}, obj1, obj2) <br>console.log(obj3); //{a: 1, b: 1} 不会改变obj1,obj2

2.2 Traversal assignment

var obj1={'a':1};
var obj2={'b':2,'c':3};
for(var key in obj2){
   if(obj2.hasOwnProperty(key)===true){  <br>   //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};

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<br>var obj = { a: 1 ,b:2};
var copyObj = Object.assign({}, obj);
console.log(copyObj); // { a: 1,b:2 }<br><br>//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。　

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

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

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!

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Detailed introduction to the installation and use of Node.js Express

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The above is the detailed content of How to use JS to merge arrays and objects. For more information, please follow other related articles on the PHP Chinese website!