檢查javascript中是否存在函數

Question

如何檢查原型函數是否存在？

多一點解釋：

正如你可以在示例代碼中看到的，我將永遠有兩個X1和X2一個commonFunction()。

我想告訴你X1和X2有他們自己的myOwnFunction()。

重要的是要注意到，第一手我不知道我會打電話給哪個功能。這就是爲什麼我需要一種動態的方式來收集這些信息。

CODE：

function FunctionMain(){}; 

FunctionMain.FunctionSub = new FunctionSub(); 

function FunctionX1() 
{ 
    FunctionX1.prototype.commonFunction = function() 
    { 
     console.log("Hello, I'm X1"); 
    } 

    FunctionX1.prototype.myOwnFunctionX1 = function() 
    { 
     console.log("This my own function"); 
    }  
} 

function FunctionX2() 
{ 
    FunctionX2.prototype.commonFunction = function() 
    { 
     console.log("Hello, I'm X2"); 
    } 

    //I don't have myOwnFunctionX2() 
} 

function FunctionSub() 
{ 
    FunctionSub.prototype.FunctionX1 = new FunctionX1(); 
    FunctionSub.prototype.FunctionX2 = new FunctionX2(); 
} 

//This call works! 
FunctionMain.FunctionSub.FunctionX1.commonFunction(); 
FunctionMain.FunctionSub.FunctionX2.commonFunction(); 


//what kind of test should I use? 
if(typeof "FunctionMain.FunctionSub.FunctionX1.myOwnFunctionX1" == "function") 
{ 
    console.log("It exists!"); 
} 

if(typeof window["FunctionMain.FunctionSub.FunctionX1.myOwnFunctionX1"] == "function") 
{ 
    console.log("It exists!"); 
} 

FIDDLE：http://jsfiddle.net/matias/FTzjW/

Answer 1

這是爲我工作的解決方案。

檢查這個jsbin（不知道爲什麼，這並不在jsfiddle工作）

全碼：

function FunctionMain(){} 

FunctionMain.FunctionSub = new FunctionSub(); 

function FunctionX1() 
{ 
    FunctionX1.prototype.commonFunction = function() 
    { 
     console.log("Hello, I'm X1"); 
    } 

    FunctionX1.prototype.myOwnFunctionX1 = function() 
    { 
     console.log("This my own function"); 
    }  
} 

function FunctionX2() 
{ 
    FunctionX2.prototype.commonFunction = function() 
    { 
     console.log("Hello, I'm X2"); 
    } 

    //I don't have myOwnFunctionX2() 
} 

function FunctionSub() 
{ 
    FunctionSub.prototype.FunctionX1 = new FunctionX1(); 
    FunctionSub.prototype.FunctionX2 = new FunctionX2(); 
} 

//This call works! 
FunctionMain.FunctionSub.FunctionX1.commonFunction(); 
FunctionMain.FunctionSub.FunctionX2.commonFunction(); 


//use this test 
function testFunction(function_to_find) 
{ 
    var context = window; 
    var functions = function_to_find.split("."); 
    var method = functions.pop(); 

    for (var i = 0; i < functions.length; i++) 
    { 
     context = context[functions[i]]; 
    } 

    return typeof context[method]; 
} 

if(testFunction("FunctionMain.FunctionSub.FunctionX1.myOwnFunctionX1") == "function") console.log("yes x1!"); 

if(testFunction("FunctionMain.FunctionSub.FunctionX2.myOwnFunctionX2") == "function") console.log("yes x2!"); 

Answer 2

這是奇怪的，不這樣做

function FunctionX2() 
{ 
    FunctionX2.prototype.commonFunction = function() 
    { 
     console.log("Hello, I'm X2"); 
    } 

    //I don't have myOwnFunctionX2() 
} 

做到這一點，而不是

var FunctionX2 = function() { 
    // constructor 
}; 

FunctionX2.prototype.commonFunction = function() { 
    console.log("Hello, I'm X2"); 
}; 

如果直接存在

typeof FunctionX2.prototype.commonFunction === 'function'; 
// => true 

或用實例

檢查

var f2 = new FunctionX2(); 
typeof f2.commonFunction === 'function'; 
// => true 

---

這裏的示威，檢查功能動態可能

var functionExists = function(receiver, functionName) { 
    return typeof receiver[functionName] === 'function'; 
}; 

var commonFunctionExists = function(receiver) { 
    return functionExists(receiver, 'commonFunction'); 
}; 

一些測試

var f1 = new FunctionX1(); 
commonFunctionExists(f1); 
// => true 

var f2 = new FunctionX2(); 
commonFunctionExists(f2); 
// => true 

var obj = new Object(); 
commonFunctionExists(obj); 
// => false