带层数的扁平化实现了下 function flatten(arr,lev) {         var arr1 = []         if(lev == 0) {             // console.log(arr,arr1,11)             arr1 = arr1.concat(arr)             // console.log(arr1,1223)         } else {             for(let i = 0; i < arr.length; i++) {                 if(Array.isArray(arr[i]) === true){                     arr1 = arr1.concat(flatten(arr[i], lev-1))                     // console.log(arr1,223)                 } else {                     arr1.push(arr[i])                 }             }         }           return arr1     }     var ary = [1,2,[3,[4,5]],6,[7,8]]     console.log(flatten(ary,2))