Simple examples of currying in JavaScript.

javascript_curry_examples_spec.js

var expect = require("expect.js"),
    allonges = require("allong.es").allong.es,
    curry = allonges.curry,
    map = allonges.map,
    compose = allonges.compose,
    identity = require('oscin.es').I;

// Example of currying in JavaScript
// See http://comp-phil.blogspot.com/2014/03/currying-in-javascript.html

var ownAdd = function(a){
  return function(b){
    return function(c){
      return a + b + c;
    }
  }
};

var addThree = function(a, b, c){return a + b + c;},
  allongesAdd = curry(addThree);

describe("Figure out how to do currying in JavaScript", function(){
  describe("Hand rolled curry add", function(){
    it("Given three numbers, we will add them all up", function(){
      expect(ownAdd(1)(2)(3)).to.be.equal(6);
    }),
    it("Given two numbers, we will get a unary function for adding numbers", function(){
      var add3 = ownAdd(1)(2);
      expect(add3(3)).to.be.equal(6);
      expect(add3(1)).to.be.equal(4);
    }),
    it("Given one number, we will get a binary function for adding numbers", function(){
      var add1 = ownAdd(1);
      expect(add1(2)(3)).to.be.equal(6);
      expect(add1(11)(1)).to.be.equal(13);
      
      var add5 = add1(4)
      expect(add5(1)).to.be.equal(6);
    });
  });
  describe("Allong.es curry add", function(){
    it("Given three numbers, addThree will add them up (make sure our lights are on)", function(){
      expect(addThree(1, 2, 3)).to.be.equal(6);
    }),
    it("Given three numbers, we will add them all up", function(){
      expect(allongesAdd(1)(2)(3)).to.be.equal(6);
      expect(allongesAdd(1, 2, 3)).to.be.equal(6); // for free!
    }),
    it("Given two numbers, we will get a unary function for adding numbers", function(){
      var add3 = allongesAdd(1)(2);
      expect(add3(3)).to.be.equal(6);
      expect(add3(1)).to.be.equal(4);
    }),
    it("Given one number, we will get a binary function for adding numbers", function(){
      var add1 = allongesAdd(1);
      expect(add1(2)(3)).to.be.equal(6);
      expect(add1(11, 1)).to.be.equal(13);  // yep, we can do this either way!
      
      var add5 = add1(4)
      expect(add5(1)).to.be.equal(6);
    });
  });
  describe("More real world examples using map from Allong.es", function(){
    var luggageCombination = [1, 2, 3, 4, 5],
        luggageMappings = map(luggageCombination);

    // see also http://www.csun.edu/~erm52178/docs-xlrs-mhts/misc-files/luggage-combination.html
    
    it("Given the identity function, the luggage will still have the same combination", function(){
      expect(luggageMappings(identity)).to.be.eql(luggageCombination);
    }),
    it("Given squared function, the luggage will have the combination squared", function(){
      var squared = function(x){return x * x;};
      expect(luggageMappings(squared)).to.be.eql([1, 4, 9, 16, 25]);
    }),
    it("Given a squared mod 10 function, the luggage will have the combination squared mod 10", function(){
      var squared = function(x){return x * x;},
          squaredMod10 = compose(function(x){return x % 10;}, squared); // Who's an idiot now?!?
      expect(luggageMappings(squaredMod10)).to.be.eql([1, 4, 9, 6, 5]);
    });
  });
});

See my blog post which goes with this gist: http://comp-phil.blogspot.com/2014/03/currying-in-javascript.html