Creating user interfaces in JavaScript can sometimes lead to a problem, especially when the interface used AJAX to load data from the server. As many actions will be event driven by the user you can find that when a user triggers lots of events all at once the browser will send out lots of AJAX requests all at once. This can easily cause bandwidth issues but can also lead to the user getting confused while they patiently await the browser to settle down and let them get on with things.

The for loop in JavaScript can be used to iterate through all items in an array or properties of an object. This makes looping through any object or array very easy. As in the following example that printing out all items in an array.

Creating a new Draggable object with the script.aculo.us framework is easy. You just create a new instance of the Draggable object with the element id to be made draggable as the first parameter and a set of options as the second.

Here is a function to create a group of radio buttons in a HTML form. The three parameters are:

Here are a few of the built in JavaScript functions available.

To get the length of a string use the length variable. This returns the number of characters in a string.

var str = 'abcdef';
str.length; // returns 6

The charAt function will return the character at the point specified in the parameter. So to get the first character of a string use:

Getting a random row from a MySQL table requires the use of the RAND() function in the ORDER BY clause of the SELECT statement. This will generate a new random number for each row and order them by that new number. In order to get a single row this is combined with the LIMIT clause to limit the result to a single row.