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 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//www.jb51.cc/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

rush: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

rush: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,<a href="https://www.jb51.cc/tag/xiugai/" target="_blank" class="keywords">修改</a>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;

})();