ZeptoJS

Zepto is a jQuery replacement, using it(Zepto) instead to speed up loading for mobile devices. Please be aware it doesn't have all of the features of jQuery and at the same time it has features that jQuery doesn't such as touch events(ie: swipe). So therefore the focus for zepto is mobile and modern browsers. So no support for the old IEs.

I found that Zepto is kinda slower than jQuery in severals case, like this one : http://jsperf.com/zepto-vs-jquery-element-creation/5