我只是试图以不同的方式理解函数中定义的变量的行为。所以我只是尝试了一些代码，并在下面的评论中得出结论。请告诉我是否理解有误。或者如果我错过了什么就添加。
我想知道如何访问在函数上声明的变量，例如functionName.variableName通过函数实例（objTempFun1和objTempFun2），就像我可以在函数内部定义方法以通过函数实例公开闭包变量一样。
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 />");
在这里找到 JSFiddle 。