javascript的设计模式实现04之Iterator

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本文介绍了一种使用JavaScript实现迭代器模式的方法，通过自定义ArrayIterator类来遍历数组，并结合MyMap类实现了键值对的查找、更新、添加及删除等操作。

Iterator模式参考图片：

代码：

var Iterator = function() {};
Iterator.prototype.first = function(){};
Iterator.prototype.next = function(){};
Iterator.prototype.isDone = function(){};
Iterator.prototype.currentItem = function(){};

var ArrayIterator = function(o) {
	var items = o;
	var curIdx = -1;
	this.first = function() {
		if (items == null || items.length < 1)
			return null;
		curIdx = 0;
		return items[0];
	};
	this.next = function() {
		if (items == null || items.length < 1)
			return null;
		if (this.isDone())
			return items[items.length - 1];
		else
			return items[curIdx++];
	};
	this.isDone = function() {
		if (items == null || items.length < 1 || items[curIdx] == null)
			return true;
		else
			return false;
	};
	this.currentItem = function() {
		if (this.isDone())
			return null;
		else
			return items[curIdx];
	};
	this.currentIdx = function() {
		return curIdx;
	};
};
ArrayIterator.prototype = new Iterator;
ArrayIterator.prototype.constructor = ArrayIterator;

var Map = function() {};
Map.prototype.createIterator = function() {};

var MyMap = function() {
	this.datas = new Array;
	this.createIterator = function() {
		return new ArrayIterator(this.datas);
	};
};
MyMap.prototype = new Map;
MyMap.prototype.constructor = MyMap;
MyMap.prototype.find = function(key) {
	var itor = this.createIterator();
	itor.first();
	var item;
	while(!itor.isDone()) {
		item = itor.currentItem();
		if (key.localeCompare(item.key) == 0)
			return item.value;
		itor.next();
	};
	return null;
};
MyMap.prototype.update = function(key, value) {
	var itor = this.createIterator();
	itor.first();
	var item;
	while(!itor.isDone()) {
		item = itor.currentItem();
		if (key.localeCompare(item.key) == 0) {
			this.datas.splice(itor.currentIdx(), 1, {key:key, value:value});			
			return true;
		}
		itor.next();
	};
	return false;
};
MyMap.prototype.add = function(key, value, ifUpdate) {
	var item = this.find(key);
	if (item != null && ifUpdate == true)
		return this.update(key, value);
	if (item == null) {
		this.datas.push({key:key, value:value});
		return true;
	}
	return false;
};
MyMap.prototype.del = function(key) {
	var itor = this.createIterator();
	itor.first();
	var item;
	while(!itor.isDone()) {
		item = itor.currentItem();
		if (key.localeCompare(item.key) == 0) {
			this.datas.splice(itor.currentIdx(), 1);			
			return item;
		}
		itor.next();
	};
	return null;
};

var o = new MyMap;
o.add("1", {a:1});
o.add("2", {a:2});
o.add("3", {a:3, b:33});
o.add("3", {a:3, b:333}, true);
o.add("3", {a:3, b:33333});
o.add("4", {a:4, c:44});
o.add("5", {a:5});
console.log(o.find("3"));
o.del("3");
console.log(o.find("3"));