数组扁平化
//1
const flat1 = (arr)=>{
return arr.reduce((pre,cur)=>{
return pre.concat(Array.isArray(cur)?flat1(cur):cur)
},[])
}
//2 toSting/split
const flat2 = (arr)=>{
return arr.toString().split(',').map(value=>Number(value))
}
//3 join/split
const flat3 = (arr)=>{
return arr.join().split(',').map(value=>Number(value))
}
//4
const flat4 = (arr)=>{
while(arr.some(value=>Array.isArray(value))){
arr = [].concat(...arr)
}
return arr
}
//5
const flat5 = (arr) =>{
while(arr.some(value=>Array.isArray(value))){
arr.flat()
}
return arr
}