Drupal 6 JavaScript and jQuery - Ebook-Cours.com

Drupal Behaviors
Currently, these aren't really buttons at all. Nothing will happen when you click
them. We need to add an event handler to these two so that they respond when
clicked. We use jQuery's click() function to add an event handler for the
click event.
The click() function takes a function as an argument. Once again, we define an
anonymous function to handle this.
Here's the event handler function that is attached to the click event:
function () {
var txtareaEle = $('#' + txtareaID).get(0);
var sel = SimpleEditor.selection;
if(sel.id == txtareaID && sel.start != sel.end) {
txtareaEle.value = SimpleEditor.insertTag(
sel.start,
sel.end,
$(this).hasClass('bold') ? 'strong' : 'em',
txtareaEle.value
);
sel.start = sel.end = -1;
}
}
Each time one of our buttons is clicked, a version of the above function will
be executed.
What do I mean by a version?
This function, as an anonymous function, is created once per button. Furthermore,
the function definition is nested within another function definition (the definition for
the anonymous function inside of each()). Each time the function is defined in the
each() loop, it takes with it the environment defined by its parent function. In short,
it's not just a function, but also a snapshot of the environment in which the function
was created.
While each version of this function does the same thing, each has access to a
different environment.
For example, txtareaID, defined in the parent function (as we just saw), is still
available inside of this function. Furthermore, the txtareaID for the function
assigned to the first text area is different than the txtareaID assigned to the second
text area. In spite of the fact that the variable name is the same, the scope of the
variable is such that one click handler retains a copy, while another click handler
retains a different copy with a different value.
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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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