JSFiddle - React, Tailwind, and code Playground

JavaScript

var input_arr = [1,2,3,4,5,6];
var exclude_index = [];
var prefix_arr = [];
function perm(arr, exclude_index, prefix_arr) {
    if(prefix_arr.length == arr.length) {
        ///got an end
        console.log(prefix_arr);
    } else {
        for(var i = 0; i < arr.length; i++) {
            //select i from arr and place it in the new array
            if(exclude_index.indexOf(i) != -1) {
                continue;
            }
            var new_exclude_index = exclude_index.slice(0);
            new_exclude_index.push(i);
            var new_prefix_arr = prefix_arr.slice(0);
            new_prefix_arr.push(arr[i]);
            perm(arr, new_exclude_index, new_prefix_arr) ;
        }
    }
}
perm(input_arr, exclude_index, prefix_arr);