Example of implementing dictionary and hash table structures corresponding to key values in JavaScript

javascript implementation of Dictionary

Programming ideas:

• The bare object datastore is used for element storage;
• Two methods for obtaining dictionary lengths are implemented, one is variable tracking and the other is real-time calculation.

Code:

 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;})();

JavaScript implementation of hash (hashtable)

Programming ideas:

• Use linked lists to solve the problem of opening the link method to solve the collision, and use the single linked list library LinkedList written by yourself (see //www.VeVB.COM/article/86394.htm before jb51);
• Use naked objects to store;
• ValuePair simple encapsulation of key-value pairs;
• Organize code in module mode;

Code:

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){ //If key already exists, modify the value to the new value currNode = currNode.next; if(currNode.element.key == key){ currNode.element.value = value; break; } } if(currNode.next == null && currNode.element.value != value){ //key does not exist, add a new value. Pay attention to the boundary value 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) { //Horner's algorithm, prime number is 37 var hashValue = 6011; for (var i = 0; i < key.length; i++) { hashValue = hashValue * 37 + key.charCodeAt(i); } return hashValue % 1019; } module.exports = Hashtable;})();