Charting library using d3.js framework

Link here.

Amazing js library to give superpowers to your css and js! A lot of features with pretty nice documentation.

Link here.

Nice ways to curve your text

Link here.

Check if your page is visible currently via javascript

Link here.

Extract and manipulate rar files using javascript !

Link here.

Preload assets(eg. images) on your page

Link here.

Know which css is going unused

Link here.

Tired of figuring out how to vertically(or horizontally) center your elements? Here's a javascript plugin!

Link here.

Easy library to make charts and graphs

Link here.

Count character, words and paragraphs entered by a user live

A very small plugin that has no dependencies.
Link here.

A plugin if you want to use excel/spreadsheet formulas.

Link here.

Write better html using HTML inspector plugin

Link here.

A javascript library, Cytoscape.js for analysis and visualization

Link here.

Learn how to efficiently handle garbage collection when working on an HTML5 game

Link here.

A javascript library to enable gamepads and joysticks in the browser.

Link here.

Load high resolution image for retina display screens

Link here.

50 Javascript libraries for charts and graphs

Link here.

Detect timezone using javascript

Link here.

Saving and accessing javascript values in json even after a page refresh !

Link here.

Yes, now it's possible to access small json key-values in javascript even after a page is refreshed using Lawnchair api.

Fundamental Javascript tutorials

Link here.
New to javascript? Here are a series of tutorials for absolute beginners