对象遍历的几种方式

for in

const obj = {name: 'wsf', age: 12, sex: '男'}
for(const key in obj) {
	console.log(obj[key], key, obj)
}

Object.keys

const obj = {name: 'wsf', age: 12, sex: '男'}
Object.keys(obj).forEach(key => {
	console.log(obj[key], key, obj)
})

自定义 forEach 方法

Object.prototype.forEach = function forEach(fn){
	for (const key in this){
		if(Object.prototype.hasOwnProperty.call(this, key)) {
			fn.call(null, this[key], key, this)
		}
	}
}

const obj = {name: 'wsf', age: 12, sex: '男'}
obj.forEach((val, key, obj) => {
	console.log(val, key, obj)
})

Array & Object forEach

function isArray(ele) {
	return Object.prototype.toString.call(ele) === "[object Array]"
}

function isObject(ele) {
	return Object.prototype.toString.call(ele) === "[object Object]"
}
function forEach(obj, fn) {
	if (isArray(obj)) {
		obj.forEach((ele, index, array) => fn.call(null, ele, index, array))
	} else if (isObject(obj)) {
		for (const key in obj) {
			if (Object.prototype.hasOwnProperty.call(obj, key)) {
				fn.call(null, obj[key], key, obj)
			}
		}
	} else {
		return
	}
}
const obj = {name:'wsf', age: 19, sex: '男'}
forEach(obj, (val, key, obj) => {
	console.log(val, key, obj)
})

const array = [1,2,3]
forEach(array, (val, index, array) => {
	console.log(val, index, array)
})