Question

I’ve seen various patterns in object creation, but upon diving into some Firefox framework Javascript, I’d noticed that they’re using a convention that I haven’t seen before and I’m hoping that someone here can either confirm my assumption or correct me:

When building a class, I’ve done this (and variations of) in the past:

function MyClass() {
    this.myPublicFunction = function() {
    };
    var myPrivateFunction = function() {
    };
}

Bound anonymous functions. Cool. This is what I’ve seen throughout most frameworks and such.

However, it seem that Mozilla does this:

function MyClass() {
    this.myPublicFunction = function MYCLASS_myPublicFunction() {
    };
    var myPrivateFunction = function MYCLASS_myPrivateFunction() {
    };
}

My assumption is that in using the latter convention, JS JIT compiles the functions, but wouldn’t pick up the first two as they’d be defined at run-time rather than parse time.

Is this assumption correct and if so, does this also apply to other JS engines or just Spidermonkey?

Answer 1

Reasons to use NFE:

• a function with a name gives more debugging information in your stack trace
• NFE are self documenting. (if you put useful information in the name).

Note that function declarations are better then NFE. (From a personal style choice)

function MyClass() {
    this.myPublicFunction = myPublicFunction;

    function myPrivateFunction() {

    }

    function myPublicFunction() {

    }
}

Also note that the word “private” is misleading, but that’s a tangent.