JavaScript中实现键值对应的字典与哈希表结构的示例
作者：zhoutk
字典或者哈希表这样的键值对应结构在其他很多语言中都有内置,非常好用,这里我们来看一下JavaScript中实现键值对应的字典与哈希表结构的示例:
字典（Dictionary）的javascript实现
编程思路：
- 使用了裸对象datastore来进行元素存储；
- 实现了两种得到字典长度的方法，一种为变量跟踪，一种为实时计算。
代码：
function(){
"use strict";
function Dictionary(){
this._size = 0;
this.datastore = Object.create(null);
}
Dictionary.prototype.isEmpty = function(){
return this._size === 0;
};
Dictionary.prototype.size = function(){
return this._size;
};
Dictionary.prototype.clear = function(){
for(var key in this.datastore){
delete this.datastore[key];
}
this._size = 0;
};
Dictionary.prototype.add = function(key, value){
this.datastore[key] = value;
this._size++;
};
Dictionary.prototype.find = function(key){
return this.datastore[key];
};
Dictionary.prototype.count = function(){
var n = 0;
for(var key in this.datastore){
n++;
}
return n;
};
Dictionary.prototype.remove = function(key){
delete this.datastore[key];
this._size--;
};
Dictionary.prototype.showAll = function(){
for(var key in this.datastore){
console.log(key + "->" + this.datastore[key]);
}
};
module.exports = Dictionary;
})();
散列（hashtable）的javascript实现
编程思路：
- 以链表来解决实现开链法来解决碰撞，并使用自己写的单链表库LinkedList（详见jb51之前的https://www.jb51.net/article/86394.htm)；
- 用裸对象来存储；
- ValuePair简单封装键值对；
- 以模块模式组织代码；
代码：
valuePair.js
(function(){
"use strict";
function ValuePair(key, value){
this.key = key;
this.value = value;
}
ValuePair.prototype.toString = function(){
return "[" + this.key + ":" + this.value + "]";
};
module.exports = ValuePair;
})();
hashtable.js
(function(){
"use strict";
var ValuePair = require("./lib/ValuePair");
var LinkedList = require("./LinkedList");
function Hashtable(){
this.table = Object.create(null);
this._size = 0;
}
Hashtable.prototype.isEmpty = function(){
return this._size === 0;
};
Hashtable.prototype.size = function(){
return this._size;
};
Hashtable.prototype.remove = function(key){
var index = hashCode(key);
if(this.table[index] == null){
return false;
}else{
var currNode = this.table[index].getHead();
while(currNode.next){
currNode = currNode.next;
if(currNode.element.key == key){
this.table[index].remove(currNode.element);
this._size--;
return true;
}
}
return false;
}
};
Hashtable.prototype.get = function(key){
var index = hashCode(key);
if(this.table[index] == null){
return null;
}else{
var currNode = this.table[index].getHead();
while(currNode.next){
currNode = currNode.next;
if(currNode.element.key == key){
return currNode.element;
}
}
return null;
}
};
Hashtable.prototype.put = function(key, value){
var index = hashCode(key);
if(this.table[index] == null){
this.table[index] = new LinkedList();
}
var currNode = this.table[index].getHead();
while(currNode.next){ //key若已经存在,修改value值为新值
currNode = currNode.next;
if(currNode.element.key == key){
currNode.element.value = value;
break;
}
}
if(currNode.next == null && currNode.element.value != value){ //key不存在,加入新值.注意边界值
this.table[index].add(new ValuePair(key,value));
this._size++;
}
return this;
};
Hashtable.prototype.display = function(){
for(var key in this.table){
var currNode = this.table[key].getHead();
while(currNode.next){
currNode = currNode.next;
console.log(currNode.element.toString());
}
}
};
/*********************** Utility Functions ********************************/
function hashCode(key) { //霍纳算法,质数取37
var hashValue = 6011;
for (var i = 0; i < key.length; i++) {
hashValue = hashValue * 37 + key.charCodeAt(i);
}
return hashValue % 1019;
}
module.exports = Hashtable;
})();