v1
4/24/2020 by Lamik 4/24/202000
Setup JavaScript
let arr = Array(1000000).fill(0).map((x,i)=> 'el-'+i);;
let i = 500000;
let el = "NEW";ready
arr.splice(i, 0, el);ready
Array.prototype.splice.apply(arr, [i, 0, el]);ready
Array.prototype.splice.call(arr, i, 0, el);ready
arr.slice(0, i).concat(el, arr.slice(i));ready
[...arr.slice(0, i), el, ...arr.slice(i)]ready
arr.reduce((s, a, j)=> (j-i ? s.push(a) : s.push(el, a), s), []);