javascript中的哈希表(hashtable)实现

javascript中的hashtable实现

javascript中没有像c#,java那样的哈希表(hashtable),
然而，javascript中的Array也只有一些类似于'哈希表'的非常简单功能, 如下： var arr = new Array();
arr['item1'] = 'the value of item 1 ';
arr['item2'] = 'the value of item 2 ';
alert(arr['item1']);
alert(arr['item2']);

但上述功能，不符我们的实际要求，另外查询遍历也不方便，我们需要在Array的基础上进行扩展，
下面我们可以用js中的数组来实现类似的hashtable的功能,

function Hashtable(){
this.clear = hashtable_clear;
this.containsKey = hashtable_containsKey;
this.containsValue = hashtable_containsValue;
this.get = hashtable_get;
this.isEmpty = hashtable_isEmpty;
this.keys = hashtable_keys;
this.put = hashtable_put;
this.remove = hashtable_remove;
this.size = hashtable_size;
this.toString = hashtable_toString;
this.values = hashtable_values;
this.hashtable = new Array();
}

function hashtable_clear(){
this.hashtable = new Array();
}

function hashtable_containsKey(key){
var exists = false;
for (var i in this.hashtable) {
if (i == key && this.hashtable[i] != null) {
exists = true;
break;
}
}
return exists;
}

function hashtable_containsValue(value){
var contains = false;
if (value != null) {
for (var i in this.hashtable) {
if (this.hashtable[i] == value) {
contains = true;
break;
}
}
}
return contains;
}

function hashtable_get(key){
return this.hashtable[key];
}

function hashtable_isEmpty(){
return (this.size == 0) ? true : false;
}

function hashtable_keys(){
var keys = new Array();
for (var i in this.hashtable) {
if (this.hashtable[i] != null)
keys.push(i);
}
return keys;
}

function hashtable_put(key, value){
if (key == null || value == null) {
throw 'NullPointerException {' + key + '},{' + value + '}';
}else{
this.hashtable[key] = value;
}
}

function hashtable_remove(key){
var rtn = this.hashtable[key];
//this.hashtable[key] =null;
this.hashtable.splice(key,1);

return rtn;
}

function hashtable_size(){
var size = 0;
for (var i in this.hashtable) {
if (this.hashtable[i] != null)
size ++;
}
return size;
}

function hashtable_toString(){
var result = '';
for (var i in this.hashtable)
{
if (this.hashtable[i] != null)
result += '{' + i + '},{' + this.hashtable[i] + '}/n';
}
return result;
}

function hashtable_values(){
var values = new Array();
for (var i in this.hashtable) {
if (this.hashtable[i] != null)
values.push(this.hashtable[i]);
}
return values;
}
Hastable类使用方法:

//实例化一个自定义的哈希表类

var hashTable = new Hashtable();

hashTable.put(0,'abc'); //0为key, 'abc'为value

hashTable.put(1,'123');
hashTable.put(2,'88a');
hashTable.put(3,'88a');

//遍历hashtable, 相当于c#和java中的foreach

for (var key in hashTable.keys()){ /* 用keys方法 */
alert(hashTable.get(key)); //按key遍历value

}

//遍历hashtable, 相当于c#和java中的foreach

for (var key in hashTable.hashtable)){ /* 用hashtable属性 */

alert(hashTable.get(key)); //按key遍历value

}

alert(hashTable.containsKey(1)); //返回true
alert(hashTable.containsKey(4)); //因为不存在key为4的，返回false

alert(hashTable.containsValue('888')); //返回true
alert(hashTable.containsValue('mobidogs')); //因为不存在value为'mobidogs'的，返回false

hashTable.remove(1); //移除key为1的元素

alert(hashTable.containsKey(1)); //因为key为1的元素已被上行的reomve()方法移除，所以返回false

//关于hastable的其它方法使用简单,读者可以自己测试 (此略)