Most of the time to search through DOM and filter text we need a jQuery Expression/filter which gives us case-insensitive result. I believe it's required to have it as a part of jQuery base-library but anyway writing your own is very simple.
I have gone through some of other implementation before writing this but here this version is complete copy of jQuery library's "contains" filter except it is case-insensitive.
In below code when it's using $(elem).text() it's calling Sizzle.getText internally which is Utility function for retreiving the text value of an array of DOM nodes.
$.extend($.expr[":"], { "contains-ci": function(elem, i, match, array) { return (elem.textContent || elem.innerText || $(elem).text() || "").toLowerCase().indexOf((match[3] || "").toLowerCase()) >= 0; } });
Here are some other nice jQuery Selectors and Expressions:
I thought let me use gist to host this tiny piece of code, may be just to make it easy to share and live as long as possible..! 
