Flatten Array Manually

flatten-array-function.md

let arr0 = [1, 3, 4, 5, [1]];
let arr1 = [1, 2, 3, [1, [2, { a: 3 }], 4, [2, 3, 4]]];

function flatten(input) {
    const stack = [...input];

    const res = [];
    let i = 0;
    while (stack.length) {
        const next = stack.pop();
        if (Array.isArray(next)) {
            stack.push(...next);
        } else if (typeof next === 'object') {
            res.push(...Object.values(next));
        } else {
            res.push(next);
        }
    }
    return res.reverse();
}

flatten(arr0);
flatten(arr1);