README.md

This sample shows you how to specify the correct externs file to use JSlim with a jQuery pseudo selector.

Running this sample

Once you have built JSlim you can compile this example by running the following command from the root of the JSlim project tree:

build/install/jslim/bin/jslim --js_output_file jquery_selector_sample/out.js --js jquery_selector_sample/main.js --lib_js libs/jquery-1.7.2.js --externs jquery_selector_sample/externs.txt

Then open the index.html file in your favorite browser.

Why is this sample special?

JSlim has many samples using jQuery, but this one is special because of the use of pseudo selectors. This sample removes a class from every other paragraph tag using the :odd pseudo selector. jQuery powers these selectors with a set of functions in the Sizzle library. The final code looks like this:

jQuery(document).ready(function() { 
    $("p:odd").removeClass("blue").removeClass("under"); 
});

This code works by calling the odd function from jQuery, but it doesn't directly reference it. The Sizzle library calls the odd function dynamically by parsing the selector string. JSlim can't follow that dynamic reference so it thinks that the odd function isn't getting called and removes it.

You need to specify an externs file for JSlim so it knows to keep the odd function.

Extern files

JSlim follows a similar convention to the Google Closure Compiler with an externs file. It's the last argument in the build command from the first section. This file lists a set of functions that JSlim should never remove. The externs file for this sample looks like:

find
TAG
odd

This preserves the odd function and the functions that support it and makes the sample work properly.