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"use strict" //启用严格模式在尝试给基本包装类型已定义的下标赋值的时候报错

const isComplexDataType = obj => (typeof obj === 'object' || typeof obj === 'function') && obj !== null

//简单实现ES6的Object.assign

const selfAssign = function (target, ...source) {

if (target == null) throw new TypeError('Cannot convert undefined or null to object')

return source.reduce((acc, cur) => {

isComplexDataType(acc) || (acc = new Object(acc)); //变成一个基本包装类型

if (cur == null) return acc; //source为null,undefined时忽略

// 遍历出Symbol属性和可枚举属性

[...Object.keys(cur), ...Object.getOwnPropertySymbols(cur)].forEach(key => {

acc[key] = cur[key]

})

return acc

}, target)

}

Object.selfAssign || Object.defineProperty(Object, 'selfAssign', {

value: selfAssign,

configurable: true,

enumerable: false,

writable: false

})

let target = {

a: 1,

b: 1

}

let obj1 = {

a: 2,

b: 2,

c: undefined

}

let obj2 = {

a: 3,

b: 3,

[Symbol("a")]: 3,

d: null

}

console.log(Object.selfAssign(target, obj1, obj2))

console.log(Object.selfAssign("abd", null, undefined))