function HFM(){

			var souce = [];

			function createNode(node){

				var obj = {

					weight:0,

					parent:-1,

					lchild:-1,

					rchild:-1,

					value:''

				};

				return Object.assign(obj,node);

			}

			this.addNode = function(node){

				//添加单词和频率（权值）

				souce.push(createNode(node));

			}

			this.createTree = function(){

				//哈夫曼树

				var HuffNode  = JSON.parse(JSON.stringify(souce));

				var n = HuffNode.length;

				var x1,x2; //两个权值最小的索引

				var m1,m2;         //两个权值最小的值

				for(var i = 0; i < n ; i++){

					m1 = m2 = Infinity;  //初始化为最大值

					x1 = x2 = -1; 

					for(var j = 0; j < n+i; j++){ //寻找两个权值最小，且父节点为-1的

						var item = HuffNode[j];

						if(item.weight  < m1 && item.parent == -1){

							m2 = m1;

							x2 = x1;

							m1 = item.weight;

							x1 = j;

						}else if(item.weight  < m2 && item.parent == -1){

							m2 = item.weight;;

							x2 = j;

						}

					}

					if(x1 != -1 && x2 != -1){

						HuffNode[x1].parent = n + i;  //更新父节点

						HuffNode[x2].parent = n + i;

						//创建一个新的节点

						HuffNode[n+i] = createNode({

							weight:m1+m2,

							lchild:x1,

							rchild:x2

						});

					}

				}

				return HuffNode;

			};

			this.getCode = function(){

				//哈夫曼编码

				var n = souce.length;

				var tree = this.createTree();

				var codes = {};

				for(var i = 0; i < n; i++){

					var p = tree[i].parent;

					var code = '';

					var c = i;

					while(p != -1){  //迭代前溯

						if(tree[p].lchild == c){

							code = 0 + code;

						}else{

							code = 1 + code;

						}

						c = p;

						p = tree[p].parent;

					}

					codes[ tree[i].value ] = code;

					console.log(tree[i].value , code);

				}

				return codes;

			}

		}

		var hfm = new HFM();

		hfm.addNode({

			weight:5,

			value:"a"

		});

		hfm.addNode({

			weight:32,

			value:"b"

		});

		hfm.addNode({

			weight:18,

			value:"c"

		});

	    hfm.addNode({

			weight:7,

			value:"d"

		});

		hfm.addNode({

			weight:25,

			value:"e"

		});

		hfm.addNode({

			weight:13,

			value:"f"

		});

		console.log(hfm.getCode())