What if the element exists in the DOM

That was described in my recent post and it describes the case when you have a particular element in the DOM tree, or if that element does not exists.

example:

HTML:
<div id="holder">
<div id="element_id">Hello World!</div>
</div>

JavaScript (jQuery):
console.log( $('#element_id').length )

this prints 1, because the element exists. In the following example is different. Read the rest of this entry »

What’s a closure

Well every javascript programer knows that a variable defined in javascript file with the var declaration is global into all javascript code.

var a = 12;
console.log(a);

that code prints 12 into the console.

Note: console object is visible in Firefox and Safari, but not in IE, and here’s used just for the test!

Here comes the closures

Let’s assume I’ve two javascript files.

file1.js:

var a = 12;

file2.js:

a = 13;

Than obviously if I print out the variable a in file2.js after that line, I’ll have the value of a equal to 13, and this will be the value of the variable a from the file1.js, because that’s obviously the same variable. Read the rest of this entry »

JavaScript libraries and OS

Particularly in that case I’m using jQuery which is enough famous, so I’m not going to introduce it, but however you can use any library, and this remains of your choice. The interesting part here is that I didn’t find a jQuery specific OS detecting plugin.

Reference to the roots: www.quirksmode.org

Well the guru PPK has the right answer, which is working with every JavaScript library … because it’s pure JavaScript itself. Read the rest of this entry »

Select the element

If you’re familiar with jQuery, which I suppose is true, you know how to select an element, for instance if there’s an element with id element_id, you do:

$('#element_id')

If the element exists in the DOM

if ( $('#element_id').length > 0 )
       console.log('the element with element_id
                    exists in the DOM');

Note: that console.log is present as console writing function under FF and Safari only.

if not …

Than $(‘#element_id’).length equals to 0

if ( $('#element_id').length == 0 )
       console.log('the element with element_id
                    don't exists in the DOM');

If you’ve to debug some script in Safari, and you’d wish to write into the javascript console, the simple advice is to use the same code as in Firefox.

console.log(object);

That’s all.