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如何动态合并两个 JavaScript 对象的属性?

我需要能够在运行时合并两个(非常简单的)JavaScript 对象。例如,我想:

var obj1 = { food: 'pizza', car: 'ford' }
var obj2 = { animal: 'dog' }

obj1.merge(obj2);

//obj1 now has three properties: food, car, and animal

有没有人有这个脚本或知道内置的方式来做到这一点?我不需要递归,我不需要合并函数,只需要平面对象上的方法。

答案

ECMAScript 2018 标准方法

你会使用对象传播

let merged = {...obj1, ...obj2};

/** There's no limit to the number of objects you can merge.
 *  Later properties overwrite earlier properties with the same name. */
const allRules = {...obj1, ...obj2, ...obj3};

ECMAScript 2015(ES6)标准方法

/* For the case in question, you would do: */
Object.assign(obj1, obj2);

/** There's no limit to the number of objects you can merge.
 *  All objects get merged into the first object. 
 *  Only the object in the first argument is mutated and returned.
 *  Later properties overwrite earlier properties with the same name. */
const allRules = Object.assign({}, obj1, obj2, obj3, etc);

(参见MDN JavaScript 参考


ES5 和早期的方法

for (var attrname in obj2) { obj1[attrname] = obj2[attrname]; }

请注意,这只会将obj2所有属性添加到obj1 ,如果您仍想使用未修改的obj1 ,则可能不是您想要的。

如果你正在使用一个遍布原型的框架,那么你必须使用像hasOwnProperty这样的检查来获得更好的功能,但是该代码适用于 99%的情况。

功能示例:

/**
 * Overwrites obj1's values with obj2's and adds obj2's if non existent in obj1
 * @param obj1
 * @param obj2
 * @returns obj3 a new object based on obj1 and obj2
 */
function merge_options(obj1,obj2){
    var obj3 = {};
    for (var attrname in obj1) { obj3[attrname] = obj1[attrname]; }
    for (var attrname in obj2) { obj3[attrname] = obj2[attrname]; }
    return obj3;
}

jQuery 还有一个实用工具: http//api.jquery.com/jQuery.extend/

取自 jQuery 文档:

// Merge options object into settings object
var settings = { validate: false, limit: 5, name: "foo" };
var options  = { validate: true, name: "bar" };
jQuery.extend(settings, options);

// Now the content of settings object is the following:
// { validate: true, limit: 5, name: "bar" }

上面的代码将改变现有的名为settings 对象


如果要在不修改任何参数的情况下创建新对象 ,请使用以下命令:

var defaults = { validate: false, limit: 5, name: "foo" };
var options = { validate: true, name: "bar" };

/* Merge defaults and options, without modifying defaults */
var settings = $.extend({}, defaults, options);

// The content of settings variable is now the following:
// {validate: true, limit: 5, name: "bar"}
// The 'defaults' and 'options' variables remained the same.

Harmony ECMAScript 2015(ES6)指定了Object.assign ,它将执行此操作。

Object.assign(obj1, obj2);

当前的浏览器支持越来越好 ,但如果您正在为没有支持的浏览器进行开发,则可以使用polyfill