Drupal 6 JavaScript and jQuery - Ebook-Cours.com

JavaScript Theming
As we have already seen, when the page is delivered and loaded, JavaScript can start
doing its thing. It can rearrange the page, add new data, hide old data, and create an
interactive environment in which the user's input can change what is displayed.
The server's theme engine is responsible for taking Drupal data and laying it out
for display. Once loaded on the client side, JavaScript can change that display. This
means even JavaScrip can become responsible for generating the look and feel of a
page. Therefore, JavaScript must be able to generate and manipulate HTML and CSS.
How does JavaScript handle this task? In the past, it handled it in one of the two
not-very-graceful ways.
The first way was to embed strings inside of application logic. This led to code that
looked something like this:
function calculateSum() {
var out = '';
var total = 0;
if (arguments.length == 0) {
out += 'Error: No data given.';
}
else if (arguments.length == 1) {
out += 'Error: Cannot sum only one number.';
}
else {
out += 'The sum is: ';
for(var i = 0; i < arguments.length; ++i) {
total += arguments[i];
}
out += new String(total) + '';
}
out += '';
document.getElementById('sum').innerHTML = out;
return total;
}
Simply speaking, the purpose of this demonstration function is to sum all of the
arguments passed to it, and then place the result inside of the element with the id sum.
Passing an arbitrary number of arguments in JavaScript
JavaScript supports passing a function, a variable number of arguments
(sometimes referred to as varargs). Every function has access to a variable
called arguments, which is an array-like object containing all of the
parameters (in order) that were passed into the function.
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This material is copyright and is licensed for the sole use by Richard Ostheimer on 18th June 2009
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