ES8(二) —— Object (keys、values、entries)

JavaScriptES6

# ES8新增对对象快速遍历的方法

# Object.keys()

  • 参数是目标对象
  • 返回的是指定对象的键组成的数组

# 返回一个数组

ES5

let grade = {
  "lilei": 96,
  "hanmeimei": 99
}

let result = []

for (let k in grade) {
  result.push(k)
}

console.log(result) //["lilei", "hanmeimei"]
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ES8

let grade = {
  "lilei": 96,
  "hanmeimei": 99
}

console.log(Object.keys(grade)) //["lilei", "hanmeimei"]
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# 条件筛选

ES5

let grade = {
  "lilei": 96,
  "hanmeimei": 99
}

let result = []

for (let k in grade) {
  if(k === 'lilei'){
    result.push(k)
  }
}

console.log(result) // ["lilei"]
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ES8

let grade = {
  "lilei": 96,
  "hanmeimei": 99
}

console.log(Object.keys(grade).filter(item => item === 'lilei')) // ["lilei"]
// 返回一个数组,之后可以对数组进行合并、替换、查找
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# Object.values()

  • 参数是目标对象
  • 返回的是值组成的数组
let grade = {
  "lilei": 96,
  "hanmeimei": 99
}

console.log(Object.values(grade)) // [96,99]
console.log(Object.values(grade).filter(item => item > 97)) //[99]
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# Object.entries()

# 可以把对象变成可遍历的对象

可以结合 ES6(十五)—— lterator 使用

let grade = {
  "lilei": 96,
  "hanmeimei": 99
}


for(let [k, v] of Object.entries(grade)){
  console.log(k,v)
}
// lilei 96
// hanmeimei 99
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# 可以传到Map中变成一个map对象进行操作

本质依旧是把对象变成可遍历的,符合lterator结构的

let grade = {
  "lilei": 96,
  "hanmeimei": 99
}
let map1 = new Map(Object.entries(grade))
map1.get("lilei") // 96
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更新时间: 2021-09-15 12:03