I prefer to use the JavaScript features availble in modern browser over using different libraries. One thing still missing in JavaScript is Promises. A good library that works in browsers (and also in NodeJS) is promisejs by Forbes Lindesey. Bluebird claims to provide better performance but I'm sticking to promisejs for now. Promises area included in EcmaScript 6 so native support is coming.
You should also have a look at CurryJS if you like to develop in the functional style.
Some helper functions I also often end-up using: source