This example helps me understand one use case of function currying - pre-applying a common argument to make code more succinct. These are two utility functions: method bolted onto the Function prototype and a curry method added to objects via the method function. To see currying in action take a look from sprayPaintCar() onwards.

Without further ado:

// Helper method taken from JS: The Good Parts
Function.prototype.method = function(name, func) {
  this.prototype[name] = func;
  return this;

// Bolt a 'curry' method onto the Function prototype that retrofits the slice method to the "arguments" array-like
object. We then can combine the arguments from the original function with the newly defined "pre-filled" function.
Function.method('curry', function() {
  var slice = Array.prototype.slice,
      args = slice.apply(arguments),
      that = this;
  return function() {
    return that.apply(null, args.concat(slice.apply(arguments)));

// Actual function we want to use in this currying example
var sprayPaintCar = function(make, colour) {
  return "Car make " + make + " has been spray painted " + colour + " colour.";

console.log(sprayPaintCar('toyota', 'red'));
// By using currying, if we are only spray painting Toyota cars then we can create a curried function for convenience.
sprayPaintAToyota = sprayPaintCar.curry('toyota');