数组拓展

// Array.from()
const divs = document.getElementsByTagName(‘div‘)
Array.from(divs).forEach(v => {
       console.log(v)
})

// Array.of()
const arry = Array.of(1,2,3)

// 实现copyWithin()
Array.prototype.myCopyWithin = function(pos,start,end){
       return this.splice(pos,end-start+1,...this.slice(start-1,end)),this }
const arry = [0,1,2,3,4,5,6,7,8,9]
console.log(arry.copyWithin(3,4,8))
console.log(arry.myCopyWithin(3,4,8))