JSFiddle - React, Tailwind, and code Playground

by lasha

JavaScript

var arr = [4, [3, 6, [9, 1, 9, [5, 1]]], 8, [5]];

function flattenArray(arr, dest){
    var flatArray = dest || [],
        arrLen = arr.length,
        i,
        item;
    
    for(i=0; i < arrLen; i++){
        var item = arr[i];
        if(item.constructor == Array){
            flattenArray(item, flatArray)
        } else {
            flatArray.push(item);
        }
    }
    
    return flatArray;
}

console.log(flattenArray(arr));