For Eclipse Juno 4.2 and Aptana Studio 3 and JQuery (jquery-1.7.2.js)
There are dozens of outdated posts on SO and elsewhere that refer to deprecated Aptana dialogs and provide information that isn't pertinent to the current Eclipse version. All I know is that for Eclipse Juno 4.2, Aptana 3 and JQuery 1.7.2, here's what works (for me, at least):
Make sure the Aptana plugin is installed and you're in the Web perspective. That's what the Aptana Studio perspective is called...it would be less confusing if they named it something that had the word 'Aptana' in it.
Make sure your default editor is 'JavaScript Source Editor'. Set this in Window -> Preferences -> General -> Editors -> File Associations and choosing the .js extension in the list. There is more than one option in the list box below. Using any other editor didn't even give me code coloring...this is the only one I could get code assist to work with.
I did this but I don't know if it was really even necessary. But I installed the JQuery ruble as below:
http://wiki.appcelerator.org/display/tis/JavaScript+Library+Support#JavaScriptLibrarySupport-jQuery%28
Then, to expound on the answer provided by majgis at the bottom of Eclipse JavaScript Editor: content assist for js files, autocompletion
:
Create a new project and add the uncompressed JQuery library by dropping jquery-1.7.2.js onto the project in the Project Explorer and selecting the Link To File option in the dialog that appeared. I linked to the jquery-1.7.2.js in the /js folder of the project root which is where the library usually goes anyway.
Drop jquery1.4.2.sdocml into the project and choose to either copy or link to the file. I copied the file into the root of the project.
Follow the SO link above for more information.