Map和Object区别

区别：

• API不通，Map可以以任意类型为key
• Map是有序结构（重要）
• Map操作同样很快

// object
// const obj = {
//	name: '张三',
//	title: 'Author'
// }
// 只能以字符串为key，且是无序格式

// map Api
const m = new Map([
	['name', '张三'],
	['title', 'Author']
])
m.set('age', 30)
m.delete('title')
m.has('name')
m.size
m.forEach(val => console.log(val))
// ...

// 以任意类型为key
const o = { p: 'Hello World' }
m.set(o, 'object key')
const fn = () {}
m.set(fn, 'fn key')
const obj1 = { name: '小红' }
const obj2 = { name: '小明' }
m.set(obj1, obj2) // 关联，但没有引用关系，保持独立

// Map是有序的并且还很快，object是无序的
const targetObj = {}
const targetMap = new Map()
for (let i = 0; i < 10000000; i++) {
  targetObj[i + ''] = i
  targetMap.set(i + '', i)
}
console.time('targetObj find')
targetObj['5000000']
console.timeEnd('targetObj find')
console.time('targetObj delete')
delete targetObj['5000000']
console.timeEnd('targetObj delete')

console.time('targetMap find')
targetMap.has('5000000')
console.timeEnd('targetMap find')
console.time('targetMap delete')
targetMap.delete('5000000')
console.timeEnd('targetMap delete')

// targetObj find: 0.009033203125 ms
// targetObj delete: 0.0029296875 ms
// targetMap find: 0.007080078125 ms
// targetMap delete: 0.001953125 ms
// Map有序与obj无序执行速度相差不多