如何动态合并两个 JavaScript 对象的属性

发布于01月01日

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

有没有一种内在的方法可以做到这一点？我不需要递归，也不需要合并函数，只需要平面对象上的方法.

推荐答案

ECMAScript 2018 Standard Method

你可以使用object spread:

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

merged现在是obj1和obj2的和.obj2中的属性将覆盖obj1中的属性.

/** 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};

下面也是此语法的MDN documentation.如果你使用的是巴别塔，你需要babel-plugin-transform-object-rest-spread插件才能工作.

ECMAScript 2015 (ES6) Standard Method

/* 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);

(见MDN JavaScript Reference)

Method for ES5 and Earlier个

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

请注意，这将简单地添加obj2到obj1的所有属性，如果您仍然想要使用未修改的obj1，那么这些属性可能不是您想要的.

如果你使用的框架在你的原型上到处都是垃圾，那么你必须通过hasOwnProperty这样的判断来获得更丰富的知识，但这些代码将适用于99%的情况.

示例功能:

/**
 * 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;
}