查看完整版本 : JS 101 - 003 spread operator

var arr = [1,2,3];
var arr2 = [...new Array(arr.length)].map((a,b)=>(a-1) === b?a:arr[b]).reduce((a,b,c)=>a.map((d,e)=>e===c?b:d),[...new Array(arr.length)]);

謝謝收看。:loveliness: