BFS

     Tree.prototype.traverse = function (callback) {
     var queue=[this];
     var n;

     while(queue.length>0) {

     n = queue.shift();
     callback(n.value);

     if (!n.children) {
     continue;
     }

    for (var i = 0; i< n.children.length; i++) {
    queue.push(n.children[i]);
       }
     }
   };