两个对象。assign和Object spread只做浅合并。
这个问题的一个例子:
// No object nesting
const x = { a: 1 }
const y = { b: 1 }
const z = { ...x, ...y } // { a: 1, b: 1 }
输出是您所期望的。然而，如果我尝试这样做:
// Object nesting
const x = { a: { a: 1 } }
const y = { a: { b: 1 } }
const z = { ...x, ...y } // { a: { b: 1 } }
而不是
{ a: { a: 1, b: 1 } }
你得到
{ a: { b: 1 } }
X被完全覆盖，因为扩展语法只覆盖了一层。这与Object.assign()相同。
有办法做到这一点吗?
当前回答
deepmerge npm包似乎是解决这个问题使用最广泛的库: https://www.npmjs.com/package/deepmerge
其他回答
如果您想合并多个普通对象(不要修改输入对象)。基于对象。分配polyfill
function isPlainObject(a) { return (!!a) && (a.constructor === Object); } function merge(target) { let to = Object.assign({}, target); for (let index = 1; index < arguments.length; index++) { let nextSource = arguments[index]; if (nextSource !== null && nextSource !== undefined) { for (let nextKey in nextSource) { // Avoid bugs when hasOwnProperty is shadowed if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) { if (isPlainObject(to[nextKey]) && isPlainObject(nextSource[nextKey])) { to[nextKey] = merge(to[nextKey], nextSource[nextKey]); } else { to[nextKey] = nextSource[nextKey]; } } } } } return to; } // Usage var obj1 = { a: 1, b: { x: 2, y: { t: 3, u: 4 } }, c: "hi" }; var obj2 = { b: { x: 200, y: { u: 4000, v: 5000 } } }; var obj3 = { c: "hello" }; console.log("result", merge(obj1, obj2, obj3)); console.log("obj1", obj1); console.log("obj2", obj2); console.log("obj3", obj3);
如果你想合并有限的深度
function isPlainObject(a) { return (!!a) && (a.constructor === Object); } function merge(target) { let to = Object.assign({}, target); const hasDepth = arguments.length > 2 && typeof arguments[arguments.length - 1] === 'number'; const depth = hasDepth ? arguments[arguments.length - 1] : Infinity; const lastObjectIndex = hasDepth ? arguments.length - 2 : arguments.length - 1; for (let index = 1; index <= lastObjectIndex; index++) { let nextSource = arguments[index]; if (nextSource !== null && nextSource !== undefined) { for (let nextKey in nextSource) { // Avoid bugs when hasOwnProperty is shadowed if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) { if (depth > 0 && isPlainObject(to[nextKey]) && isPlainObject(nextSource[nextKey])) { to[nextKey] = merge(to[nextKey], nextSource[nextKey], depth - 1); } else { to[nextKey] = nextSource[nextKey]; } } } } } return to; } // Usage var obj1 = { a: 1, b: { x: 2, y: { t: 3, u: 4, z: {zzz: 100} } }, c: "hi" }; var obj2 = { b: { y: { u: 4000, v: 5000, z: {} } } }; var obj3 = { c: "hello" }; console.log('deep 0', merge(obj1, obj2, obj3, 0)); console.log('deep 1', merge(obj1, obj2, obj3, 1)); console.log('deep 2', merge(obj1, obj2, obj3, 2)); console.log('deep 2', merge(obj1, obj2, obj3, 4));
// copies all properties from source object to dest object recursively
export function recursivelyMoveProperties(source, dest) {
for (const prop in source) {
if (!source.hasOwnProperty(prop)) {
continue;
}
if (source[prop] === null) {
// property is null
dest[prop] = source[prop];
continue;
}
if (typeof source[prop] === 'object') {
// if property is object let's dive into in
if (Array.isArray(source[prop])) {
dest[prop] = [];
} else {
if (!dest.hasOwnProperty(prop)
|| typeof dest[prop] !== 'object'
|| dest[prop] === null || Array.isArray(dest[prop])
|| !Object.keys(dest[prop]).length) {
dest[prop] = {};
}
}
recursivelyMoveProperties(source[prop], dest[prop]);
continue;
}
// property is simple type: string, number, e.t.c
dest[prop] = source[prop];
}
return dest;
}
单元测试:
describe('recursivelyMoveProperties', () => {
it('should copy properties correctly', () => {
const source: any = {
propS1: 'str1',
propS2: 'str2',
propN1: 1,
propN2: 2,
propA1: [1, 2, 3],
propA2: [],
propB1: true,
propB2: false,
propU1: null,
propU2: null,
propD1: undefined,
propD2: undefined,
propO1: {
subS1: 'sub11',
subS2: 'sub12',
subN1: 11,
subN2: 12,
subA1: [11, 12, 13],
subA2: [],
subB1: false,
subB2: true,
subU1: null,
subU2: null,
subD1: undefined,
subD2: undefined,
},
propO2: {
subS1: 'sub21',
subS2: 'sub22',
subN1: 21,
subN2: 22,
subA1: [21, 22, 23],
subA2: [],
subB1: false,
subB2: true,
subU1: null,
subU2: null,
subD1: undefined,
subD2: undefined,
},
};
let dest: any = {
propS2: 'str2',
propS3: 'str3',
propN2: -2,
propN3: 3,
propA2: [2, 2],
propA3: [3, 2, 1],
propB2: true,
propB3: false,
propU2: 'not null',
propU3: null,
propD2: 'defined',
propD3: undefined,
propO2: {
subS2: 'inv22',
subS3: 'sub23',
subN2: -22,
subN3: 23,
subA2: [5, 5, 5],
subA3: [31, 32, 33],
subB2: false,
subB3: true,
subU2: 'not null --- ',
subU3: null,
subD2: ' not undefined ----',
subD3: undefined,
},
propO3: {
subS1: 'sub31',
subS2: 'sub32',
subN1: 31,
subN2: 32,
subA1: [31, 32, 33],
subA2: [],
subB1: false,
subB2: true,
subU1: null,
subU2: null,
subD1: undefined,
subD2: undefined,
},
};
dest = recursivelyMoveProperties(source, dest);
expect(dest).toEqual({
propS1: 'str1',
propS2: 'str2',
propS3: 'str3',
propN1: 1,
propN2: 2,
propN3: 3,
propA1: [1, 2, 3],
propA2: [],
propA3: [3, 2, 1],
propB1: true,
propB2: false,
propB3: false,
propU1: null,
propU2: null,
propU3: null,
propD1: undefined,
propD2: undefined,
propD3: undefined,
propO1: {
subS1: 'sub11',
subS2: 'sub12',
subN1: 11,
subN2: 12,
subA1: [11, 12, 13],
subA2: [],
subB1: false,
subB2: true,
subU1: null,
subU2: null,
subD1: undefined,
subD2: undefined,
},
propO2: {
subS1: 'sub21',
subS2: 'sub22',
subS3: 'sub23',
subN1: 21,
subN2: 22,
subN3: 23,
subA1: [21, 22, 23],
subA2: [],
subA3: [31, 32, 33],
subB1: false,
subB2: true,
subB3: true,
subU1: null,
subU2: null,
subU3: null,
subD1: undefined,
subD2: undefined,
subD3: undefined,
},
propO3: {
subS1: 'sub31',
subS2: 'sub32',
subN1: 31,
subN2: 32,
subA1: [31, 32, 33],
subA2: [],
subB1: false,
subB2: true,
subU1: null,
subU2: null,
subD1: undefined,
subD2: undefined,
},
});
});
});
这里是@Salakar的答案的一个不可变(不修改输入)版本。如果你在做函数式编程，这很有用。
export function isObject(item) {
return (item && typeof item === 'object' && !Array.isArray(item));
}
export default function mergeDeep(target, source) {
let output = Object.assign({}, target);
if (isObject(target) && isObject(source)) {
Object.keys(source).forEach(key => {
if (isObject(source[key])) {
if (!(key in target))
Object.assign(output, { [key]: source[key] });
else
output[key] = mergeDeep(target[key], source[key]);
} else {
Object.assign(output, { [key]: source[key] });
}
});
}
return output;
}
function isObject(obj) {
return obj !== null && typeof obj === 'object';
}
const isArray = Array.isArray;
function isPlainObject(obj) {
return isObject(obj) && (
obj.constructor === Object // obj = {}
|| obj.constructor === undefined // obj = Object.create(null)
);
}
function mergeDeep(target, ...sources){
if (!sources.length) return target;
const source = sources.shift();
if (isPlainObject(source) || isArray(source)) {
for (const key in source) {
if (isPlainObject(source[key]) || isArray(source[key])) {
if (isPlainObject(source[key]) && !isPlainObject(target[key])) {
target[key] = {};
}else if (isArray(source[key]) && !isArray(target[key])) {
target[key] = [];
}
mergeDeep(target[key], source[key]);
} else if (source[key] !== undefined && source[key] !== '') {
target[key] = source[key];
}
}
}
return mergeDeep(target, ...sources);
}
// test...
var source = {b:333};
var source2 = {c:32, arr: [33,11]}
var n = mergeDeep({a:33}, source, source2);
source2.arr[1] = 22;
console.log(n.arr); // out: [33, 11]
我想介绍一个相当简单的ES5替代方案。该函数获得2个参数——目标和源，必须为“object”类型。Target将是结果对象。Target保留其所有原始属性，但它们的值可能会被修改。
function deepMerge(target, source) {
if(typeof target !== 'object' || typeof source !== 'object') return false; // target or source or both ain't objects, merging doesn't make sense
for(var prop in source) {
if(!source.hasOwnProperty(prop)) continue; // take into consideration only object's own properties.
if(prop in target) { // handling merging of two properties with equal names
if(typeof target[prop] !== 'object') {
target[prop] = source[prop];
} else {
if(typeof source[prop] !== 'object') {
target[prop] = source[prop];
} else {
if(target[prop].concat && source[prop].concat) { // two arrays get concatenated
target[prop] = target[prop].concat(source[prop]);
} else { // two objects get merged recursively
target[prop] = deepMerge(target[prop], source[prop]);
}
}
}
} else { // new properties get added to target
target[prop] = source[prop];
}
}
return target;
}
例:
如果target没有source属性，则target获取source属性; 如果目标有source属性，而target & source没有 两个对象(4个中的3个)，目标的属性被覆盖; 如果target确实有一个source属性，并且它们都是对象/数组(剩余1种情况)，那么递归发生合并两个对象(或两个数组的连接);
还要考虑以下几点:
Array + obj = Array Obj + array = Obj Obj + Obj = Obj(递归合并) Array + Array = Array (concat)
它是可预测的，支持基本类型以及数组和对象。我们可以合并两个对象，我认为我们可以通过reduce函数合并两个以上的对象。
看一个例子(如果你想的话，也可以玩一下):
var a = { "a_prop": 1, "arr_prop": [4, 5, 6], "obj": { "a_prop": { "t_prop": 'test' }, "b_prop": 2 } }; var b = { "a_prop": 5, "arr_prop": [7, 8, 9], "b_prop": 15, "obj": { "a_prop": { "u_prop": false }, "b_prop": { "s_prop": null } } }; function deepMerge(target, source) { if(typeof target !== 'object' || typeof source !== 'object') return false; for(var prop in source) { if(!source.hasOwnProperty(prop)) continue; if(prop in target) { if(typeof target[prop] !== 'object') { target[prop] = source[prop]; } else { if(typeof source[prop] !== 'object') { target[prop] = source[prop]; } else { if(target[prop].concat && source[prop].concat) { target[prop] = target[prop].concat(source[prop]); } else { target[prop] = deepMerge(target[prop], source[prop]); } } } } else { target[prop] = source[prop]; } } return target; } console.log(deepMerge(a, b));
有一个限制-浏览器的调用堆栈长度。现代浏览器会在一些真正深层的递归中抛出错误(想想成千上万的嵌套调用)。此外，您还可以自由地处理像数组+对象等情况，因为您希望添加新的条件和类型检查。
