What are all the advantages of jQuery?
My answer to What are all the advantages of jQuery? on Quora
jQuery’s API is astonishingly well designed. It’s extremely consistent once you learn its rules (e.g. methods often take one argument to read a value and two arguments to set one, e.g. .css(), .attr(), .width(), .height()) and its functionality is so complete that the last few major releases of the library have hardly added any new methods at all.
jQuery’s performance improves noticeably with every release, with the API staying exactly the same.
Even discounting browser differences, jQuery is an enormous improvement on the DOM. It makes DOM manipulation extremely easy, which means it’s much easier to implement things using progressive enhancement—taking existing DOM elements on the page and enhancing their behaviour.