How to create a Neural Network in JavaScript in only 30 lines of code

But before we look at the code, let's go through the very basics of neural networks. The first building block of a neural network is, well, neurons. A neuron is like a function, it takes a few inputs and returns an output. There are many different types of neurons. Our network is going to use sigmoid neurons, which take any given number and squash it to a value between 0 and 1. The circle below illustrates a sigmoid neuron.