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我是看着Static variables in JavaScript，我發現了一些我以前也見過，該函數的定義和函數定義的函數原型更新後：爲什麼在函數定義之外引用靜態變量（函數屬性）？
function MyClass() { // constructor function
//function definition here
}
//now add a (static?) method *outside* the function definition
MyClass.prototype.publicMethod = function() {
alert(this.publicVariable);
};
//add a static property *outside* the function definition
MyClass.staticProperty = "baz";
我的問題是 - 爲什麼不將它們定義在函數定義裏面，像這樣：
function MyFunc(){
MyFunc.staticVar = 1;
//static method showing static var
MyFunc.showVarStatic = function(){
alert(MyFunc.staticVar);
}
//instance method referring to static var
this.showVarInstance = function(){
alert(MyFunc.staticVar);
}
//instance method - doesn't change static var
this.inc1 = function(){
this.staticVar += 1;//no such property
}
//static method, changes var
this.inc2 = function(){
MyFunc.staticVar += 1;//increments static property
}
}
這似乎在IE8，FF和Chrome中的預期行爲。這僅僅是個人喜好/風格的東西嗎？我喜歡它，因爲我的整個功能都包含在大括號中。
[編輯：做更多的閱讀和試驗後，我有更好的理解如何JavaScript函數是構造器，它們從如何不同。例如，C＃類 - 這裏的一些代碼我用來證明這一點]
//this is deceiving, notSoStaticVar won't exist until MyFunc1 has been run
//and then it will be reset whenever MyFunc1 (a constructor) is run
function MyFunc1(){
MyFunc1.notSoStaticVar = "I belong to MyFunc1";
this.instanceVar = "I belong to instances of MyFunc1";
}
//this code will be run inline one time,
//so the static property of MyFunc2 will exist
//(I like how all the functionality is in one code block, but it's kind of messy)
MyFunc2 = (function(){
var temp = function(){
this.instanceVar = "I belong to an instance of MyFunc2";
}
temp.staticVar = "I belong to MyFunc2";
return temp;
})();
//this seems to be equivalent to MyFunc2, but the code is cleaner
MyFunc3 = function(){
}
MyFunc3.prototype.instanceVar = "I belong to an instance of MyFunc3";
MyFunc3.staticVar = "I belong to MyFunc3";
//tests
console.log(MyFunc1.notSoStaticVar);//undefined!
var a = new MyFunc1();
console.log(MyFunc1.notSoStaticVar);//"I belong to MyFunc1"
console.log(a.instanceVar);//"I belong to instances of MyFunc1"
MyFunc1.notSoStaticVar = "I will be changed when another instance of MyFunc1 is created";
console.log(MyFunc1.notSoStaticVar);//"I will be changed when another instance of MyFunc1 is created"
var b = new MyFunc1();
console.log(MyFunc1.notSoStaticVar);//"I belong to MyFunc1" - was reset by constructor!
//now test MyFunc2
console.log(MyFunc2.staticVar);//"I belong to MyFunc2"
MyFunc2.staticVar = "I am not affected by the construction of new MyFunc2 objects";
var c = new MyFunc2();
console.log(c.instanceVar);//"I belong to an instance of MyFunc2"
console.log(MyFunc2.staticVar);//"I am not affected by the construction of new MyFunc2 objects"
//now test MyFunc3
console.log(MyFunc3.staticVar);//"I belong to MyFunc3"
MyFunc3.staticVar = "I am not affected by the construction of new MyFunc3 objects";
var d = new MyFunc3();
console.log(d.instanceVar);//"I belong to an instance of MyFunc3"
console.log(MyFunc3.staticVar);//"I am not affected by the construction of new MyFunc3 objects"
//interesting
console.log(c);//"temp" <-- not really intuitive!
console.log(d);//"MyFunc3" <-- makes sense
從您在示例中編寫的內容中，我想了解原型如何工作可能會有所幫助。您是否熟悉原型繼承的工作方式，或者對快速瀏覽有幫助？ –
我已經閱讀過有關原型，但從來沒有真正與它們混淆過 - 並沒有真正想過原型和靜態變量（或方法）之間的關係。在進一步的思考和實驗中，我可以看到如何使用原型並獲得某種靜態變量的惰性初始化，但該變量將始終由一個實例初始化......我從C＃透視圖，並意識到一些有趣的差異。我的例子中的 – Aerik