Here is a link to an Open Source JavaScript library that allows you to train neural networks in your browser. It was created by Andrej Karpathy, a PhD student at Stanford University and is currently community maintained.
It currently supports:
- Common Neural Network modules (fully connected layers, non-linearities)
- Classification (SVM/Softmax) and Regression (L2) cost functions
- Ability to specify and train Convolutional Networks that process images
- An experimental Reinforcement Learning module, based on Deep Q Learning.
Project site: http://cs.stanford.edu/people/karpathy/convnetjs/
Github: https://github.com/karpathy/convnetjs