javascript singleton question

Question

I just read a few threads on the discussion of singleton design in javascript. I\'m 100% new to the Design Pattern stuff but as I see since a Singleton by definition won\'t

Answer 1

The point of using the "pseudo constructor" is that it creates a new variable scope. You can declare local variables inside the function that are available inside any nested functions but not from the global scope.

There are actually two ways of doing it. You can call the function with new like in your example, or just call the function directly. There are slight differences in how you would write the code, but they are essentially equivalent.

Your second example could be written like this:

var singleton = new function () {
    var privateVariable = 42; // This can be accessed by dothis and dothat

    this.dothis = function () {
        return privateVariable;
    };

    this.dothat = function () {};
}; // Parentheses are allowed, but not necessary unless you are passing parameters

or

var singleton = (function () {
    var privateVariable = 42; // This can be accessed by dothis and dothat

    return {
        dothis: function () {
            return privateVariable;
        },

        dothat: function () {}
    };
})(); // Parentheses are required here since we are calling the function

You could also pass arguments to either function (you would need to add parentheses to the first example).