Filipe Sabella

A collegue of mine, Vinicius Gomes, exposes in this blog post reasons to have one line if blocks.

Following up with the discussion he started, I would like to show a technique to apply that concept in a more literate way in JavaScript.

One way to enforce this pratice and end up having more readable code is to extend the JS Function object, adding a behavior that is found in other languages, such as Ruby.

Paraphrasing his example:

function died() {
	return tries > 10;
}

function gameOver() {
	alert("You lose :(");
}

With these two functions, we would normally write something along the lines of:

if (died()) gameOver();

But we can expand the language and write something like:

gameOver.if(died());

Unfortunatelly “if” is a keyword in JS, so we have to improvise. We can search for suitable alternatives:

gameOver.when(died());
gameOver.givenThat(died());

I don’t really like the “when” word, since it could mean the scheduling of a task, but for now it’s the shortest implementation I could think of without recurring to “_if”.

Implementing this is quite simple:

Function.prototype.when = function(bool) {
	if (bool) return this();
}

Or the shorter way:

Function.prototype.when = function(bool) {
	return bool ? this() : undefined;
}

Following this line of thinking we can also easily implement “unless”:

Function.prototype.unless = function(bool) {
	return !bool ? this() : undefined;
}

But what if our function has parameters?
We can do this:

var validateContactForm = function() {
	return validate($('#contactForm'));
}
validateContactForm.when(validationIsEnabled);

Or the shorter way using function currying:

var validateContactForm = validate.curry($('#contactForm'));
validateContactForm.when(validationIsEnabled);

What are your thoughts about this?

This entry was posted on Friday, October 8th, 2010 at 22:56 and is filed under javascript. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.