JavaScript设计模式之单体模式全面解析

/* 最基本的单体模式 */ 
var her = {
name: 'Anna',
sex: 'women',
say: function(){
// 一些处理逻辑......
},
doing: function(){
// 另一些处理函数......
} 
}

var box = {
width: 0,
height: 0,
getArea: function(){
return this.width * this.width; // js中对象成的访问必须是显示的，即this是不能省略的
},
init: function(w, h){
// width = w;
// height = h;这种方式相当于定义了两个全局变量，（没加var声明的变量为全局变量）
// 并不是对对象width和height的赋值
// 下面是正确的
this.width = w;
this.height = h;
}
} //box划分了一个命名空间，命名空间里的变量只在空间里有效

var box = {
width:0,
height:0,//单体的变量
getArea:function(){
return width * height;// width，height其实并不是单体的变量，而是在init中定义的全局变量
}
init:function(w,h){
width = w;
height = h;
}
}// init中width，height其实并不是单体的变量
window.onload = function(){
var init = box.getArea();
alert(init);
}

var box = {
width:0,
height:0,
getArea:function(){
return width * height;
},
init:function(w,h){
width = w;
height = h;
}
}
window.onload = function(){
width = 0;
height = 0;
//or box.init(0,0);
var init = box.getArea();
alert(init);
}

var box = {
width: 0,
height: 0,
getArea: function(){
return width * height;//js中对象成的访问必须是显示的，即this是不能省略的
},
init:function(w,h){
width = w;
height = h;
}
}//这里的width，height其实并不是单体的对象
window.onload = function(){
width = 0;
height = 0;
var width = box.getArea();
alert(width);
}

var box = {
width: 2,
height: 2,
getArea: function(){
return this.width * this.height;/ /js中对象成的访问必须是显示的，即this是不能省略的
},
init:function(w,h){
this.width = w;
this.height = h;
}
}
window.onload = function(){
width = 0; // 不会影响单体中的局部变量也就是命名空间
height = 0; // 不会影响单体中的局部变量也就是命名空间
var width = box.getArea();
alert(width);
}

var her = (function(){
var name = 'Anna';
var sex = 'women';
return {
getArea: function(){
return name + 'is a' + sex;
},
init:function(b){
name = b;
}
}
})();
window.onload = function(){
her.name = 'Jock'; // 无法访问
alert(ger.getArea());
her.init('Lous');
alert(her.getArea());
}

// 利用单体的分支技术来定义XHR（XMLHttpRequest）对象,必须要用闭包才可以实现
var XHR = (function(){
//The three branches
var standard = {
cXHR:function(){
return new XMLHttpRequest();
} 
};
var activeXNew = {
cXHR:function(){
return new ActiveXObject('Msxml2.XMLHttp');
} 
};
var activeXOld = {
cXHR:function(){
return new ActiveXObject('Microsoft.XMLHttp');
} 
};
//To assign(分配) the branch, try each method;return whatever doesn't fail
var testObject;
try{
testObject = standard.cXHR();
return standard;// return this branch if no error was thrown 
}catch(e){
try{
testObject = activeXNew.cXHR();
return activeXNew;
}catch(e){
try{
testObject = activeXOld.cXHR();
return activeXOld;
}catch(e){
throw new Error('Create the XMLHttpRequestObject failed!'); 
}
}
}
})();
window.onload = function(){
alert(XHR.cXHR());
}