Tag Archives: javascript

What make JavaScript closures work?

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Closures again

Most of the JavaScript developer don’t even know what a JS closure is and that’s why Crockfrod is so angry. Yes, it’s true, most of the “developers” just copy and paste the code without even know how it works. OK, just in breve the closure is an anonymous function, which thus helps you define a pseudo namespace, as you may know that in a function everything is visible inside it and only there.

function myFunc() {
    var a = 10;
}

The code above makes the variable a to be visible only inside the function. But as you know there must be a function call to make “all this code work”.

myFunc();

However you can make an anonymous function – or a closure, where the function is with no name and is called once the code has been processed. The right syntax is like so:

(function() { var a = 10; })();

Why and how?

The question is: why and how that works? Why this syntax is correct?

Hint

A tiny hint is that you can make the following line working:

var myFunc = function(){ var a = 10; }();

Pay attention to this syntax and the assignment is what makes all this working.

JavaScript inheritance example

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JavaScript and inheritance

Almost for everybody the JavaScript way of implementing inheritance is odd. For a typical programmer it should look more C or Java like, but is not. However to give you a breve example, I’d like to make two objects, and to make the second one to inherit from the first. Thus I’d like to show how neither parent or child objects interact once they have been instanciated.

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	var parent = function() {};
	parent.prototype = {
		name : 'parent',
		m : 1,
		a : function() {
			console.log(this.name + ': ' + this.m);
		},
		setM : function( value ) {
			this.m = value;
		}
	};
 
	var child = function() {};
	child.prototype = new parent;
	child.prototype.name = 'child';
 
	var parentObj = new parent();
	var childObj = new child();
 
	parentObj.a();
	parentObj.setM(12);
 
	childObj.a();
	childObj.setM(3);
 
	parentObj.a();
	childObj.a();

However this describes the ability to make complex JavaScript inheritance patterns. The complete source’s here.

CSS selectors – new look over them

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How do you select?

When it comes to CSS selectors, most of us are using the most familiar selectors by id or class name. Something like:

.my-class {}
#my-id {}

But as you can see in most of the big JavaScript libraries, such as jQuery, you can improve the selection of element/s by using complex selector syntax.

Do you know the syntax?

Maybe yes, but maybe not! As I stumbled upon an interesting article on http://css-tricks.com
The Skinny on CSS Attribute Selectors.
The good part is that now you can use this powerful selector syntax to improve CSS.

Browsers

Because this is the most interesting part – yes it is supported by MSIE, and no – not before IE7, be careful if you’d like to support it.