如何动态合并两个JavaScript对象的属性？

Question

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

有没有人为此提供脚本或知道内置的方式来执行此操作？我不需要递归，也不需要合并函数，只需合并平面对象上的方法即可。

Answer 1

ECMAScript 2018标准方法

您将使用对象传播：

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

merged现在是obj1和的并集obj2。中的属性obj2将覆盖中的属性obj1。

/** 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};

这也是此语法的MDN文档。如果您正在使用babel，则需要babel-plugin-transform-object-rest-spread插件才能正常工作。

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);

ES5和更早版本的方法

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

请注意，这会简单地添加的所有属性obj2，以obj1这可能不是你想要什么，如果你仍然想使用未修改obj1。

如果您使用的框架覆盖了您的所有原型，那么您必须对诸如的检查更为精通hasOwnProperty，但是该代码将在99％的情况下都能正常工作。

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;
}