数字转字符串/字符串转数字

let num = 15
let s = num + '' // number to string
let n = +s // string to number

填充数组

let filledArray = new Array(10).fill(null).map((item, idx)=> ({'name' : 'value' + idx}))
// filledArray = [{"name":"value0"},{"name":"value1"}]

对象的动态属性

let dynamic = "value"
let user = {
    id: 1,
    [dynamic]: "other value"
}
// user = {id: 1, value: 'other value'}

删除重复项

let array = [100, 23, 23, 23, 23, 67, 45]
let outputArray = Array.from(new Set(array))
//outputArray = [100, 23, 67, 45]

数组转对象

let arr = ["value1", "value2", "value3"]
let arrObject = {...arr}
// arrObject = {0: 'value1', 1: 'value2', 2: 'value3'}

对象转数组

let n
umber = {
  one: 1, 
  two: 2,
}
let key = Object.keys(numbers) // key = [ 'one', 'two' ]
let value = Object.values(numbers)  // value = [ 1, 2 ]
let entry = Object.entries(numbers) // entry = [['one' : 1], ['two' : 2]]

使用 ^ 检查数字是否不相等

let a = 1234
if(a^123) {
  console.log('not equal')
}
// 输出：not equal

循环对象

const userObj = {
   shiyu: 32,
   zhuzl: 36  
};

// 方法一 - 获取对象 keys 后循环
Object.keys(userObj).forEach(key => userObj[key]++)
console.log(userObj) // { shiyu: 33, zhuzl: 37 }

// 方法二：实用 for ..in 循环
for(let key in userObj){
   userObj[key]++
}
console.log(userObj) // { shiyu: 34, zhuzl: 38 }

对象键按插入顺序存储

const obj = {
  name: "zhuzl",
  age: 36,
  address: "湖南省长沙市",
  profession: "前端开发工程师"
}
console.log(Object.keys(obj)) // name, age, address, profession