有三种方法可以做到这一点：-

方法1：-

// using spread ...
    let obj1 = {
        ...obj2
    };

方法2：-

// using  Object.assign() method
let obj1 = Object.assign({}, obj2);

方法3：-

// using JSON
let obj1 = JSON.parse(JSON.stringify(obj2));

我扩展了David Coallier的方法：

增加了合并多个对象的可能性支持深层对象override参数（如果最后一个参数是布尔值，则检测到）

如果覆盖为false，则不会覆盖任何属性，但会添加新的财产。

用法：obj.merge（合并…[，覆盖]）；

这是我的代码：

Object.defineProperty(Object.prototype, "merge", {
    enumerable: false,
    value: function () {
        var override = true,
            dest = this,
            len = arguments.length,
            props, merge, i, from;

        if (typeof(arguments[arguments.length - 1]) === "boolean") {
            override = arguments[arguments.length - 1];
            len = arguments.length - 1;
        }

        for (i = 0; i < len; i++) {
            from = arguments[i];
            if (from != null) {
                Object.getOwnPropertyNames(from).forEach(function (name) {
                    var descriptor;

                    // nesting
                    if ((typeof(dest[name]) === "object" || typeof(dest[name]) === "undefined")
                            && typeof(from[name]) === "object") {

                        // ensure proper types (Array rsp Object)
                        if (typeof(dest[name]) === "undefined") {
                            dest[name] = Array.isArray(from[name]) ? [] : {};
                        }
                        if (override) {
                            if (!Array.isArray(dest[name]) && Array.isArray(from[name])) {
                                dest[name] = [];
                            }
                            else if (Array.isArray(dest[name]) && !Array.isArray(from[name])) {
                                dest[name] = {};
                            }
                        }
                        dest[name].merge(from[name], override);
                    } 

                    // flat properties
                    else if ((name in dest && override) || !(name in dest)) {
                        descriptor = Object.getOwnPropertyDescriptor(from, name);
                        if (descriptor.configurable) {
                            Object.defineProperty(dest, name, descriptor);
                        }
                    }
                });
            }
        }
        return this;
    }
});

示例和测试用例：

function clone (obj) {
    return JSON.parse(JSON.stringify(obj));
}
var obj = {
    name : "trick",
    value : "value"
};

var mergeObj = {
    name : "truck",
    value2 : "value2"
};

var mergeObj2 = {
    name : "track",
    value : "mergeObj2",
    value2 : "value2-mergeObj2",
    value3 : "value3"
};

assertTrue("Standard", clone(obj).merge(mergeObj).equals({
    name : "truck",
    value : "value",
    value2 : "value2"
}));

assertTrue("Standard no Override", clone(obj).merge(mergeObj, false).equals({
    name : "trick",
    value : "value",
    value2 : "value2"
}));

assertTrue("Multiple", clone(obj).merge(mergeObj, mergeObj2).equals({
    name : "track",
    value : "mergeObj2",
    value2 : "value2-mergeObj2",
    value3 : "value3"
}));

assertTrue("Multiple no Override", clone(obj).merge(mergeObj, mergeObj2, false).equals({
    name : "trick",
    value : "value",
    value2 : "value2",
    value3 : "value3"
}));

var deep = {
    first : {
        name : "trick",
        val : "value"
    },
    second : {
        foo : "bar"
    }
};

var deepMerge = {
    first : {
        name : "track",
        anotherVal : "wohoo"
    },
    second : {
        foo : "baz",
        bar : "bam"
    },
    v : "on first layer"
};

assertTrue("Deep merges", clone(deep).merge(deepMerge).equals({
    first : {
        name : "track",
        val : "value",
        anotherVal : "wohoo"
    },
    second : {
        foo : "baz",
        bar : "bam"
    },
    v : "on first layer"
}));

assertTrue("Deep merges no override", clone(deep).merge(deepMerge, false).equals({
    first : {
        name : "trick",
        val : "value",
        anotherVal : "wohoo"
    },
    second : {
        foo : "bar",
        bar : "bam"
    },
    v : "on first layer"
}));

var obj1 = {a: 1, b: "hello"};
obj1.merge({c: 3});
assertTrue(obj1.equals({a: 1, b: "hello", c: 3}));

obj1.merge({a: 2, b: "mom", d: "new property"}, false);
assertTrue(obj1.equals({a: 1, b: "hello", c: 3, d: "new property"}));

var obj2 = {};
obj2.merge({a: 1}, {b: 2}, {a: 3});
assertTrue(obj2.equals({a: 3, b: 2}));

var a = [];
var b = [1, [2, 3], 4];
a.merge(b);
assertEquals(1, a[0]);
assertEquals([2, 3], a[1]);
assertEquals(4, a[2]);


var o1 = {};
var o2 = {a: 1, b: {c: 2}};
var o3 = {d: 3};
o1.merge(o2, o3);
assertTrue(o1.equals({a: 1, b: {c: 2}, d: 3}));
o1.b.c = 99;
assertTrue(o2.equals({a: 1, b: {c: 2}}));

// checking types with arrays and objects
var bo;
a = [];
bo = [1, {0:2, 1:3}, 4];
b = [1, [2, 3], 4];

a.merge(b);
assertTrue("Array stays Array?", Array.isArray(a[1]));

a = [];
a.merge(bo);
assertTrue("Object stays Object?", !Array.isArray(a[1]));

a = [];
a.merge(b);
a.merge(bo);
assertTrue("Object overrides Array", !Array.isArray(a[1]));

a = [];
a.merge(b);
a.merge(bo, false);
assertTrue("Object does not override Array", Array.isArray(a[1]));

a = [];
a.merge(bo);
a.merge(b);
assertTrue("Array overrides Object", Array.isArray(a[1]));

a = [];
a.merge(bo);
a.merge(b, false);
assertTrue("Array does not override Object", !Array.isArray(a[1]));

我的equals方法可以在这里找到：JavaScript中的对象比较

这会将obj合并为“默认”def。obj优先于两者中存在的任何对象，因为obj被复制到def中。还要注意，这是递归的。

function mergeObjs(def, obj) {
    if (typeof obj == 'undefined') {
        return def;
    } else if (typeof def == 'undefined') {
        return obj;
    }
    for (var i in obj) {
        if (obj[i] != null && obj[i].constructor == Object) {
            def[i] = mergeObjs(def[i], obj[i]);
        } else {
            def[i] = obj[i];
        }
    }
    return def;
}

a = {x : {y : [123]}}
b = {x : {z : 123}}
console.log(mergeObjs(a, b));
// {x: {y : [123], z : 123}}

顺便说一句，你们正在做的是覆盖财产，而不是合并。。。

这就是JavaScript对象区域真正合并的方式：只有to对象中不是对象本身的键才会被from覆盖。其他一切都将被真正合并。当然，您可以将此行为更改为不覆盖任何存在的内容，例如仅当to[n]未定义时，等等…：

var realMerge = function (to, from) {

    for (n in from) {

        if (typeof to[n] != 'object') {
            to[n] = from[n];
        } else if (typeof from[n] == 'object') {
            to[n] = realMerge(to[n], from[n]);
        }
    }
    return to;
};

用法：

var merged = realMerge(obj1, obj2);

ECMAScript 2018标准方法

您可以使用对象扩散：

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

merged现在是obj1和obj2的并集。obj2中的财产将覆盖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};

这里还有此语法的MDN文档。如果您正在使用babel，则需要@babel/plugin提议对象rest spread插件才能工作（该插件包含在ES2018中的@babel/preset-env中）。

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及更早版本的方法

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

请注意，这将简单地将obj2的所有属性添加到obj1中，如果您仍然希望使用未修改的obj1，那么这可能不是您想要的。

如果你使用的是一个在你的原型上到处都是垃圾的框架，那么你必须通过hasOwnProperty这样的检查来获得更高的效率，但这段代码在99%的情况下都是有效的。

示例函数：

/**
 * 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;
}

对于使用Node.js的用户，有一个NPM模块：Node.extend

安装：

npm install node.extend

用法：

var extend = require('node.extend');
var destObject = extend(true, {}, sourceObject);
// Where sourceObject is the object whose properties will be copied into another.