Question

I can call parse method of Date object directly as follows:

    alert(Date.parse("March 21, 2012"));

However I cannot do this:

    alert(Date.getTime()); // TypeError: Date.getTime is not a function

That is how I get it working:

    alert(new Date().getTime()); // works well

So why can’t I call Date.getTime() directly like Date.parse()?

Underlying Question: I have written a class and I want to use some of its methods directly like Date.parse() above.

Answer 1

As others have pointed out, JavaScript uses prototypes to defined instance methods. You can however defined static methods as shown below. I am not trying to define the whole Date object here, but rather show how its instance and static functions are defined.

// constructor defined here
function Date() {
    // constructor logic here
}

// this is an instance method
DateHack.prototype.getTime = function() {
    return this.time_stamp;
}

// this method is static    
Date.parse = function(value) {
    // do some parsing
    return new Date(args_go_here);
}