通過函數實例訪問JS函數變量

Question

我只是想通過不同的方式理解函數中定義的變量的行爲。所以我剛剛嘗試了一些代碼，並在下面作出評論。請告訴我是否理解錯誤。或者，如果我錯過了任何東西，請加上

我想知道我怎麼能訪問像functionName.variableName通過功能情況（objTempFun1和objTempFun2）函數聲明的變量就像我可以定義內部功能的方法，通過功能情況暴露閉包變量。

function tempFun() { 
    this.val1 = "this.var1"; 
    var val2 = "var var2"; //locally scoped var, not added to function instance nor to the prototype 

    this.getLocalVar = function() { 
     return val2; 
    }; 

    this.setLocalVar = function (arg) { 
     val2 = arg; 
    }; 
} 

tempFun.prototype.val3 = "fun.proto.var3"; 
tempFun.val4 = "fun.var4"; 

var objTempFun1 = new tempFun(); 
var objTempFun2 = new tempFun(); 

/*----------------------------------------------------------------------- 
     Variables defined as `this.variableName` 
     1. Are declared on prototype 
     2. Have separate values across instances 
     3. Cannot be accessed on function itself 
     -----------------------------------------------------------------------*/ 
document.write("<br />obj1-this.var1: " + objTempFun1.val1 + "<br />"); 
document.write("obj2-this.var1: " + objTempFun2.val1 + "<br />"); 
document.write("fun-this.var1: " + tempFun.val1 + "<br />"); 

objTempFun1.val1 = "this.var1x"; 
objTempFun2.val1 = "this.var1y"; 
document.write("obj1-this.var1: " + objTempFun1.val1 + "<br />"); 
document.write("obj2-this.var1: " + objTempFun2.val1 + "<br />"); 

/*----------------------------------------------------------------------- 
     Variables defined inside function as `var variableName` 
     1. Are closure-scoped; defined neither on function nor on prototype 
     2. Have separate values across function instances 
     3. Can only be accessed through function instance by adding methods on 
      a prototype (as above getLocalVar and setLocalVar methods) 
     -----------------------------------------------------------------------*/ 
document.write("obj1-var var2: " + objTempFun1.val2 + "<br />"); 
document.write("obj2-var var2: " + objTempFun2.val2 + "<br />"); 
document.write("fun-var var2: " + tempFun.val2 + "<br />"); 
document.write("obj1-printLocalVar: " + objTempFun1.getLocalVar() + "<br />"); 
document.write("obj2-printLocalVar: " + objTempFun2.getLocalVar() + "<br />"); 
objTempFun1.setLocalVar("var var2x"); 
objTempFun2.setLocalVar("var var2y"); 
document.write("obj1-printLocalVar: " + objTempFun1.getLocalVar() + "<br />"); 
document.write("obj2-printLocalVar: " + objTempFun2.getLocalVar() + "<br />"); 

/*----------------------------------------------------------------------- 
     Variables defined as `functionName.prototype.variablename` 
     1. Are declared on prototype 
     2. Have separate values across function instances 
     3. Cannot be accessed on function itself 
     -----------------------------------------------------------------------*/ 
document.write("obj1-this.proto.var3: " + objTempFun1.val3 + "<br />"); 
document.write("obj2-this.proto.var3: " + objTempFun2.val3 + "<br />"); 
document.write("fun-this.proto.var3: " + tempFun.val3 + "<br />"); 
objTempFun1.val3 = "fun.proto.var3x"; 
objTempFun2.val3 = "fun.proto.var3y"; 
document.write("obj1-this.proto.var3: " + objTempFun1.val3 + "<br />"); 
document.write("obj2-this.proto.var3: " + objTempFun2.val3 + "<br />"); 

/*------------------------------------------------------------------------ 
     Variables defined as `functionName.variablename` 
     1. Become member of function (or say 'F'unction instance, which is tempFun) 
      not the function instances (which are objTempFun1 & objTempFun2 above) 
     2. Cannot be accessed on function instances 
     ------------------------------------------------------------------------*/ 
document.write("obj1-fun.var4: " + objTempFun1.val4 + "<br />"); 
document.write("obj2-fun.var4: " + objTempFun2.val4 + "<br />"); 
document.write("fun-fun.var4: " + tempFun.val4 + "<br />"); 

尋找JSFiddle here。

Answer 1

constructor property提供對構建對象的函數的訪問。