Dev test. A browser / production ready implementation of a flatten array function.

recursive-flatmap.js

function flattenArray(array) {
  var flattened = [];
  function loop(array) {
    for (var i=0; i < array.length; i++) {
      var value = array[i];
      if (typeof value === 'object' && value.constructor === Array) {
        loop(value);
      } else {
        flattened.push(value);
      }
    }
  }
  loop(array);
  return flattened;
}
var myArrayOfArrays = [ [ 1, 2, 3 ], [ 12, 13, 14, [ 90, 91, 92] ] ];
flattenArray(myArrayOfArrays); // [1, 2, 3, 12, 13, 14, 90, 91, 92]