Category tree ( 'trie' ) to be used with d3's treemap

category.js

/*
  Category-tree
  Search time: O(n)
  Insert time: O(n)
*/


if (!Array.prototype.find) {
  Object.defineProperty(Array.prototype, 'find', {
    enumerable: false,
    configurable: true,
    writable: true,
    value: function(predicate) {
      if (this == null) {
        throw new TypeError('Array.prototype.find called on null or undefined');
      }
      if (typeof predicate !== 'function') {
        throw new TypeError('predicate must be a function');
      }
      var list = Object(this);
      var length = list.length >>> 0;
      var thisArg = arguments[1];
      var value;

      for (var i = 0; i < length; i++) {
        if (i in list) {
          value = list[i];
          if (predicate.call(thisArg, value, i, list)) {
            return value;
          }
        }
      }
      return undefined;
    }
  });
};

var Category_tree = function() {
};

Category_tree.prototype = (function() {

  var tree = {};
  tree.children = [];

  return {
    Constructor: Category_tree,
    insert: function(string, category, parent) {
      if (tree.children.length === 0) {
        tree.name = category;
        tree.children.push({data: string});
        return;
      }
      categoryParent = Category_tree.prototype.find(parent || category);
      if (typeof parent !== 'undefined') {
        var exists = false;
        parent = categoryParent;
        parent.find(function(e) {
          if (e.name == category) {
            exists = true;
            parent = e;
          }
        });
        if (!exists) {
          parent.push({name: category});
          parent.find(function(e) {
            if (e.name == category) {
              parent = e;
            }
          });
        }
      } else {
        parent = tree;
        parent.name = category;
      }
      if (typeof parent.children == 'undefined') {
        parent.children = [];
      }
      parent.children.push({data: string});

    },
    toString: function() {
      return tree;
    },
    find: function(category) {
      var parent = tree.children,
          stack  = [],
          found  = false;
      while(1) {
        parent.find(function(e) {
          if (e.name == category) {
            parent = e;
            found  = true;
          }
          if (typeof e.children !== 'undefined') {
            stack.push(e.children);
          }
        });
        if (stack.length >= 1) {
          parent = stack.pop();
        } else {
          break;
        }
      }
      return (found) ? parent : tree.children;
    }
  };
})();