The JavaScript Math.round() function will round a decimal to the nearest whole number, but I found that I needed was to round a number to the nearest 10. So after a bit of thinking I realised that I could divide the value by 10, round it using the round() function and then multiply the result by 10.

If you are familiar with PHP you will have come across the for loop at some point. When learning JavaScript it is important to remember that it also has the ability to do the equivalent of the PHP forloop.

The following snippet shows the creation of an array of things that can't be referenced by a normal for loop due to the odd numbering of the keys.

If you are running a JavaScript example page you can use the following function that will take the last script element on the page and print it out in a code tag. It uses JQuery to do the work, so you will need to include that library before using this function.

I came across a really nice looking plugin for JQuery the other day that allowed you to select part of an image. This plugin is called JCrop.

The isNaN() function (NaN stands for Not a Number) can be useful if you are looking at form inputs or similar and is used to detect if a value is not a number. For example, the following code shows the output of isNaN() on two variables.

Strictly speaking the Google Ajax libraries don't contain only Ajax libraries, but they are very useful for a variety of reasons. Google host a variety of different JavaScript libraries which you can link to on your pages rather than download the library and host it on your server. You can use MooTools, JQuery, Prototype/Scriptaculous, Dojo and even the Yahoo! User Interface Library.

How To Use Them

Using the Google Ajax libraries on your own site is quite easy, and you can do it in a number of different ways.