let arr = [...'abcdefghij'.repeat(100000)]; // 1M elements
let idx = 500000;
delete arr[idx];
arr.splice(idx,1);
var rest = arr.slice(idx + 1 || arr.length);
arr.length = idx < 0 ? arr.length + idx : idx;
arr.push.apply(arr, rest);
arr.slice(0,idx).concat(arr.slice(idx + 1));
arr.filter((a,i) => i !== idx);