是否可以在node.js原型定义的函数中访问私有变量？

Question

Consider the following code snippet:

function C1() {
    // private variable in the constructor
    a = 1;
}

C1.prototype.f1 = function() {
console.log( "a=" +  a );
}

C1.prototype.f2 = function() {
    a = 2;
    process.nextTick( this.f1 );
}

o = new C1();
o.f1();
o.f2();

The output observed is:

a=1
a=2

I thought private variables aren't accessible outside of the Constructor function ?

Answer 1

In JavaScript, a variable declared without the "var" keyword has global scope. In the browser this is achieved by attaching the variable to the window object (not sure how it works in Node). If you would like a private variable accessible to your object, try a closure around the object constructor and prototype declaration.