Code examples of shallow cloning and deep cloning of JS objects

This article brings you code examples about shallow cloning and deep cloning of JS objects. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Shallow Clone

Look at the code first:

/**
 * 浅克隆 克隆传入对象，只克隆一层
 * @param {any} source
 */
function shallowClone(source) {
    var tiaget = createEctype(source);  //创建一个副本
    // 将原对象的所有属性值赋值到新对象上
    for (var property in source) {
        if (source.hasOwnProperty(property)) {
            tiaget[property] = source[property];
        }
    }
    /**
    * 创建副本
    * @param {any} source
    */
    function createEctype(source) {
        var newObject = {};
        if (Array.isArray(source))
            newObject = [];
        return newObject;
    }

    return tiaget;
}

Execute the test:

var a={a1:1,a2:2,a3:[1,2,3]};
 var b={b1:1,b2:2,b3:[4,5,6]}
 a.b=b;
 b.a=a;
 a.a4=[a,b];
 b.b4=[a,b];
 a.fn=function(){console.log(this.b);};
 
 var newa=shallowClone(a);

The test code defines a self-referential object

a===a.a4[0];    // true
a===a.b.a;    // true

Execute the shallowClone method to obtain a copy of object a newa

a === newa;              // false
newa ===  newa.a4[0];    // false
newa ===   newa.b.a;     // false
a === newa.a4[0];        // true
a === newa.b.a;          // true

Test execution speed:

/**
获取传入方法在规定时间内执行次数

示例：
var test = function(){

};
runTime(test,1)
表示test方法 在1秒中执行了6819005次
**/

/**
 * 获取传入方法在规定时间内执行次数
 * @param {any} fn 执行的方法
 * @param {any} time 规定的时间，单位为秒
 */
function runTime(fn, time) {
    var startTime = Date.now();
    var count = 0;
    while (Date.now() - startTime < time * 1000) {
        fn.call();
        count++;
    }
    return count;
}

Deep Clone

Code:

/**
 * 深克隆
 * 
 * 示例：
 * var a={a1:1,a2:2,a3:[1,2,3]};
 * var b={b1:1,b2:2,b3:[4,5,6]}
 * a.b=b;
 * b.a=a;
 * a.a4=[a,b];
 * b.b4=[a,b];
 * a.fn=function(){console.log(this.b);return this.b;};
 * 
 * var newa=deepClone(a);
 * newa.a1=123;
 * newa.fn();
 */
function deepClone(source) {
    this.objKeyCache = [];      // 对象缓存
    this.objValueCache = [];    // 对象克隆缓存

    this.clone = function (source) {
        var target = createEctype.call(this, source);
        for (var property in source) {
            if (source.hasOwnProperty(property)) {
                var value = source[property];
                if (typeof value === "number"
                    || typeof value === "boolean"
                    || typeof value === "symbol"
                    || typeof value === "string"
                    || typeof value === "function"
                    || typeof value === "undefined"
                    || value === null)
                    target[property] = value;
                else if (typeof value === "object") {
                    // 如果源对象在对象缓存中存在，就用对象克隆缓存中的值赋值
                    var index = this.objKeyCache.indexOf(value);
                    if (index >= 0)
                        target[property] = this.objValueCache[index];   
                    else {
                        target[property] = this.clone( value);
                    }
                }
                else
                    throw "未知数据类型" + (typeof value);
            }
        }

        return target;
    };
    /**
     * 创建副本
     * @param {any} source
     */
    function createEctype(source) {
        var target = {};
        if (Array.isArray(source))
            target = [];
        this.objKeyCache.push(source);
        this.objValueCache.push(target);
        return target;
    }
    var newObject = this.clone(source);
    // 释放缓存，防止内存溢出
    this.objKeyCache = [];
    this.objValueCache = [];
    return newObject;
}

Execution test:

var a={a1:1,a2:2,a3:[1,2,3]};
var b={b1:1,b2:2,b3:[4,5,6]}
a.b=b;
b.a=a;
a.a4=[a,b];
b.b4=[a,b];
a.fn=function(){console.log(this.b);return this.b;};

var newa=deepClone(a);

a === newa;            // false
newa === newa.a4[0]    // true
newa === newa.b.a;     // true
a === newa.a4[0];      // false
a === newa.b.a;        // false

##Test execution speed:

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