tree-map.js

/**
  *
  * Implement a `map` method on this Tree class, using pseudoclassical instantiation.
  *
  * Map accepts a mapping function as its only argument. It traverses the tree,
  * passing each node's value into the mapping function, and generates a new
  * tree containing the results.
  *
  * So `map` should return a tree with the same structure, and different values,
  * but it should NOT modify the tree that was passed in.
  *
  * Example:
  *   var root1 = new Tree(1);
  *   var branch2 = root1.addChild(2);
  *   var branch3 = root1.addChild(3);
  *   var leaf4 = branch2.addChild(4);
  *   var leaf5 = branch2.addChild(5);
  *   var leaf6 = branch3.addChild(6);
  *   var leaf7 = branch3.addChild(7);
  *   var newTree = root1.map(function (value) {
  *     return value * 2;
  *   })
  *  newTree.value // 2
  *  newTree.children[0].value // 4
  *  newTree.children[1].value // 6
  *  newTree.children[0].children[1].value // 10
  *  newTree.children[1].children[1].value // 14
  *  root1.value // still 1
  */

var Tree = function (value){
    this.value = value; 
    this.branches = []; 
}

Tree.prototype.addBranch = function(value){
    var newBranch = new Tree(value); 
    this.branches.push(newBranch); 
}

Tree.prototype.map = function(cb){
    var newTree = new Tree(cb(this.value)); 

    for(var i = 0; i < this.branches.length; i++){
        newTree.branches.push(this.branches[i].map(cb));
    }


    return newTree; 


}


//---Building the Trees---

var oldTree = new Tree(3); 
oldTree.addBranch(5); 

var youngTree = oldTree.map(function(value){
    return value * 2; 
})