array.md

数组/json

数组

扩展

var a=[1,2]
var b = [...a,3]
console.log(b) //1,2,3

map,reduce,filter,forEach

都不会改变原数组

map 映射

let arr = [1,2,3,43,5464,46,12]
let arr2 = arr.map(item=>item>=60)
console.log(arr2)
// [ false, false, false, false, true, false, false ]

filter 过滤

let arr = [1,2,3,43,5464,46,12]
let arr2 = arr.filter(item=>item%2)
console.log(arr2) //[ 1, 3, 43 ]

forEach 遍历

let arr = [1,2,3,43,5464,46,12]
let sum=0
arr.forEach(item=>{
    sum+=item
})
console.log(sum) //5571

reduce 汇总

let arr = [1,2,3,43,5464,46,12]
let sum = arr.reduce((tmp,item,index)=>{
    return tmp+item
})
console.log(sum) //5571

from

let str = '123123'
Array.from(str).forEach(item=>console.log(item)) //123123
Array.prototype.slice.call(str).forEach(item=>console.log(item))
//123123

[...str].forEach(item=>console.log(item)) 

json

简写 省略function

let a = 1
let b = 2
let json_1 = {a,b}
console.log(json_1) //{ a: 1, b: 2 }

//对象里函数简写
let json_2 = {
    a : 1,
    b : 2,
    show(){
        console.log(a+b)
    }
}
json_2.show() //3