1+ //1.最简单的实现方法
2+ var Singleton = function ( name ) {
3+ this . name = name ;
4+ this . instance = null ;
5+ } ;
6+
7+ Singleton . prototype . getName = function ( ) {
8+ alert ( this . name ) ;
9+ } ;
10+
11+ Singleton . getInstance = function ( name ) {
12+ if ( ! this . instance ) {
13+ this . instance = new Singleton ( ) ;
14+ }
15+ return this . instance ;
16+ } ;
17+
18+ var a = Singleton . getInstance ( 'seven1' ) ;
19+ var b = Singleton . getInstance ( 'seven2' ) ;
20+ alert ( a === b ) ; // true
21+
22+ //或者
23+ var Singleton = function ( name ) {
24+ this . name = name ;
25+ }
26+
27+ Singleton . prototype . getName = function ( ) {
28+ alert ( this . name ) ;
29+ }
30+
31+ Singleton . getInstance = ( function ( ) {
32+ var instance = null ;
33+ return function ( name ) {
34+ if ( ! instance ) {
35+ instance = new Singleton ( 'name' ) ;
36+ }
37+ return instance ;
38+ }
39+ } ) ( ) ;
40+
41+ var a = Singleton . getInstance ( 'seven1' ) ;
42+ var b = Singleton . getInstance ( 'seven2' ) ;
43+ alert ( a === b ) ; // true
44+
45+ //2.透明的单例模式。上述简单的单例模式并不透明，必须要知道Singleton对象有getInstance方法可以创造单例，并不能直接new
46+ //下面代码负责在页面中创建唯一的div节点
47+ var CreatDiv = ( function ( ) {
48+ var instance ;
49+ var CreatDiv = function ( html ) {
50+ if ( instance ) {
51+ return instance ;
52+ }
53+ this . html = html ;
54+ this . init ( ) ;
55+ return instance = this ;
56+ } ;
57+
58+ CreatDiv . prototype . init = function ( ) {
59+ var div = document . createElement ( 'div' ) ;
60+ div . innerHTML = this . html ;
61+ document . body . appendChild ( div ) ;
62+ } ;
63+ return CreatDiv ;
64+ } ) ( ) ;
65+
66+ var a = new CreatDiv ( 'seven1' ) ;
67+ var b = new CreatDiv ( 'seven2' ) ;
68+
69+ alert ( a === b ) ; //true
70+
71+ //虽然上述例子实现了单例透明，但是singleton构造函数没有做到职责单一，一个方法干了两件事情，第一，是创建对象和
72+ //执行初始化init方法，第二是保证只有一个对象
73+ //用代理模式实现单例模式可解决此问题
74+ var CreatDiv = function ( html ) {
75+ this . html = html ;
76+ this . init ( ) ;
77+ } ;
78+
79+ CreatDiv . prototype . init = function ( ) {
80+ var div = document . createElement ( 'div' ) ;
81+ div . innerHTML = this . html ;
82+ document . body . appendChild ( div ) ;
83+ } ;
84+
85+ //接下来引入代理类ProxySingetonCreateDiv
86+ var ProxySingetonCreateDiv = ( function ( ) {
87+ var instance ;
88+ return function ( ) {
89+ if ( ! instance ) {
90+ instance = new CreatDiv ( html ) ;
91+ }
92+ return instance ;
93+ }
94+ } ) ( ) ;
95+
96+ var a = new ProxySingetonCreateDiv ( 'seven1' ) ;
97+ var b = new ProxySingetonCreateDiv ( 'seven2' ) ;
98+
99+ alert ( a === b ) ;
0 commit comments