Recursion Example

flatten.js

/**
 * A Little example of recursion
 **/

(function(){
  var flatten = function(toFlatten){
    var flatArr = [],
        result,
        tmp;

    if (typeof(toFlatten) !== 'undefined' && toFlatten instanceof Array){
      for(var i = 0; i < toFlatten.length; ++i){
        if(toFlatten[i] instanceof Array){
          tmp = flatArr;
          result = tmp.concat(flatten(toFlatten[i]));
          flatArr = result;
        } else {
          flatArr.push(toFlatten[i]);
          result = flatArr; 
        }
      }
    } else { 
      return null;
    }

    return result;
  }

  console.log( flatten( [1,2,3,4,5,6] ) ); //-> [1, 2, 3, 4, 5, 6]
  console.log( flatten( [1,2,3,4,5,6, [1] ] ) ); //-> [1, 2, 3, 4, 5, 6, 1]
  console.log( flatten( [ {}, [1,2,3,4,5,6] ] ) ); //-> [Object, 1, 2, 3, 4, 5, 6]
  console.log( flatten( [ [1], [1,2,3] ] ) ); //-> [1, 1, 2, 3]
  console.log( flatten( [ [1], [1,2,3], [1] ] ) ); //-> [1, 1, 2, 3, 1]
  console.log( flatten( [ [1,[1,2,3,[1,2,3,[1,2,3]]]], [1,2,3], [1] ] ) ); //-> [1, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1]
  console.log( flatten( [ ['a',['b',2,3,['c',2,3,[true,2,3]]]], [1,2,3], [1] ] ) ); //-> ["a", "b", 2, 3, "c", 2, 3, true, 2, 3, 1, 2, 3, 1]
  console.log( flatten( [ ['a',['b',2,3,['c',2,3,[true,2,3]]]], [1,(function(){return false;})(),3], [1] ] ) ); //-> ["a", "b", 2, 3, "c", 2, 3, true, 2, 3, 1, false, 3, 1]
})();