Iterative solution for flattening n-th nested arrays in Javascript

Question

Can anyone show me an iterative solution for the following problem? I solved it recursively but struggled with an iterative solution. (Facebook Technical Interv

Answer 1

Works, but not recommended:

var flatten = function(input) {
    return eval("[" + JSON.stringify(input).
    replace(/\[/g,"").replace(/\]/g,"") + "]");
}