function Huffman(str) {	// 需要编码的字符串	this.str = str;	// 键和频率映射表	this.keyCountMap = null;	// 编码和键的映射表	this.codeKeyMap = {};	// 键和编码的映射表	this.keyCodeMap = {};		// 哈夫曼树节点列表	this.nodeList = null;	// 哈夫曼树根节点	this.root = null;	// 哈夫曼编码后的01序列	this.code = null;}Huffman.prototype.cal =  function cal() {	str = this.str;	var map = {};	var i = 0;	while(str[i]) {		map[str[i]] ? map[str[i]]++ : (map[str[i]] = 1);		i++;	}	this.keyCountMap = map;}Huffman.prototype.sort = function sort() {	map = this.keyCountMap;	var result = [];	for (key in map) {		if(map.hasOwnProperty(key)) {			var obj = {				key: key,				val: map[key]			};			result.push(new Node(null, null, obj));		}	}	this.nodeList = result.sort(function(x,y){
   return x.data.val > y.data.val});}function Node(left, right, data) {	this.left = left;	this.right = right;	this.data = data;}Huffman.prototype.makeTree = function makeTree() {	var i = 0;	var len = this.nodeList.length;	var node1;	var node2;	var parentNode;	var table = this.nodeList;	while(table.length > 1) {		parentNode = new Node(table[i], table[i+1], {key: null, val: table[i]['data'].val + table[i+1]['data'].val});		table.splice(i,2);		table.unshift(parentNode);		table.sort(function(x,y){
   return x.data.val > y.data.val});	}	this.root = table[0] || new Node();	return this.root;}Huffman.prototype.traversal = function traversal(tree, code) {	if (tree.left !== null) {		traversal.call(this,tree.left, code + '0');	} else {		this.keyCodeMap[tree.data.key] = code;	}	if (tree.right !== null) {		traversal.call(this, tree.right,code + '1');	} else {		this.keyCodeMap[tree.data.key] = code;	}}Huffman.prototype.encode = function encode() {	this.cal();	this.sort();	var root = this.makeTree();	this.traversal(root, '');	var ret = this.keyCodeMap;	var i = 0;	var result = '';	var str = this.str;	while(str[i]) {		result += ret[str[i++]];	}	this.code = result;	console.log('encode:' + result);	return result}Huffman.prototype.reverseMap = function reverseMap() {	var ret = this.keyCodeMap;	var result = {};	for (key in ret) {		if(ret.hasOwnProperty(key)) {			result[ret[key]] = key;		}	}	this.codeKeyMap = result;	return result;}Huffman.prototype.decode = function decode() {	var i = 0;	var result = '';	var data = '';		var map = this.reverseMap();		var str = this.code;	while(str) {		result += str[i++];		if (result in map) {			data += map[result];			str = str.replace(new RegExp("^"+result),'');			result = '';			i = 0;		}	}	console.log("decode:" + data)}Huffman.prototype.encodeBase64 = function() {	try {		var base64 = btoa(this.code);		return base64;	} catch(e) {		return '';	}}var str = 'ew qew qd ef 24 gf ewr getElementsByTagName';var huffman = new Huffman(str)huffman.encode(str)huffman.decode();huffman.encodeBase64();```原始版```function cal(str) {	if (typeof str !== 'string' || str.length < 1) {		return;	}	var map = {};	var i = 0;	while(str[i]) {		map[str[i]] ? map[str[i]]++ : (map[str[i]] = 1);		i++;	}	return map;}function sort(map) {	map = map || {};	var result = [];	for (key in map) {		if(map.hasOwnProperty(key)) {			var obj = {				key: key,				val: map[key]			};			result.push(new Node(null, null, obj));		}	}	return result.sort(function(x,y){
   return x.data.val > y.data.val});}function Node(left, right, data) {	this.left = left;	this.right = right;	this.data = data;}function makeTree(table) {	var i = 0;	var len = table.length;	var node1;	var node2;	var parentNode;	while(table.length > 1) {		parentNode = new Node(table[i], table[i+1], {key: null, val: table[i]['data'].val + table[i+1]['data'].val});		table.splice(i,2);		table.unshift(parentNode);		table.sort(function(x,y){
   return x.data.val > y.data.val});	}	return table;}function encode(str, ret) {	if (typeof str !== 'string' || str.length < 1) {		return;	}	var i = 0;	var result = '';	while(str[i]) {		result += ret[str[i++]];	}	return result}function reverseRet(ret) {	var result = {};	for (key in ret) {		if(ret.hasOwnProperty(key)) {			result[ret[key]] = key;		}	}	return result;}function decode(str, ret) {	var i = 0;	var result = '';	var data = '';	var map = reverseRet(ret);	while(str) {		result += str[i++];		if (result in map) {			data += map[result];			str = str.replace(new RegExp("^"+result),'');			result = '';			i = 0;		}	}	console.log(data)}function traversal(tree, code, ret) {	if (tree.left !== null) {		traversal(tree.left, code + '0', ret);	} else {		ret[tree.data.key] = code;	}	if (tree.right !== null) {		traversal(tree.right,code + '1', ret);	} else {		ret[tree.data.key] = code;	}}var ret = {};var str = 'ew qew qd ef 24 gf ewr getElementsByTagName';traversal(makeTree(sort(cal(str)))[0],'', ret)decode(encode(str, ret), ret)btoa(encode(str,ret))复制代码