Javascript is a programming or scripting language primarily used for client-sided programming in web browsers. It can also be used as a server-side programming language but this is generally used less often. Javascript was originally created by Netscape for their browser Netscape Navigator, and is now an implementation of the ECMAScript standard. It is typically used in web browsers for form validation, floating navigation, AJAX and other nifty things to make web pages more interactive.
JSON data can be retrieved using AJAX from a server either using jQuery’s .ajax() function or the shorthand $.getJSON() function. If you have retrieved a JSON string without having jQuery decode it automatically using one of these functions, the string can also be parsed into a regular data array using the $.parseJSON() function.
This post shows how to populate a select box based on the value of the another, by getting JSON data with jQuery from a PHP script that gets the data from a MySQL database.
jQuery’s $.getScript() function is a shorthand wrapper to $.ajax() which easily allows remote Javascript to be loaded into the current page.
jQuery’s .offset() method returns an offset containing the top and left co-ordinates of the element top-left position relative to the document as a whole. There’s is also a .position() method which is supposed to return the offset relative to the offset parent but for me it always returns the same co-ordinates as .offset(). Maybe I’m doing something wrong with .position()…
Rather than working out the engine and version with Javascript for doing stuff that may work differently in different browsers, it’s better to use feature detection instead. jQuery has the $.support property which has a number of flags to indicate the presence of various features or bugs. I’ll look at a couple of the more useful flags here, but be sure to read the documentation for full details about all the properties.
While you ideally shouldn’t use browser detection to choose whether or not to render something in a particular fashion, jQuery does provide the capability to work out which browser renderingengine and version is being used with $.browser. There is also $.support which provides information about what the rendering engine supports and I will look at that in a later post.