An answer to a programming test from CitrusByte in Javascript.

array_flatten.js

/*
 *  Flattens a nested array into a one-dimentional array of the exact same order
 *  
 *  @param {Array} arr
 *  @return {Array} result
 */
function flattenArray(arr) {
  // Internal function to flatten the input array recursively
  function flattenArrayRecursively(arr, result) {
    for(let i = 0; i < arr.length; i++) {
      let element = arr[i];
      if(Array.isArray(element)){
        flattenArrayRecursively(element, result);
      } else {
        result.push(element);
      }
    }
  }
  
  let result = []; 
  flattenArrayRecursively(arr, result);
  return result;
}