functional programming in javascript

Since summer I've been studing functional programming, first of all I started with clojure, later continued to javascript. Actually I studied some functional programming concepts and I applied into javascript, like map, reduce, foreach, monads, ...

Of course been doing tdd, althoguh the tests are not very expressives.

The code lives here.
Some examples of tests

describe("combine filter, map & reduce", function(){
 it("return the result of combination of filter, mal and reduce", function(){
  var data = [1,2,3,4,5,6];
  var resultExpected = 15;

  var result = reduce(
       map(
        filter(
         data, functionForFilter
        ), 
        functionForMap
       ), 
       0, functionForReduce
      );

  expect(resultExpected).to.eql(result);
 });
 function functionForMap(y){
  return y + 1;
 }
 function functionForFilter(x){
  return x % 2 == 0;
 }
 function functionForReduce(acumulative, z){ 
  return acumulative + z;
 }
});

describe("PipeLine object", function(){
 it("make pipe line through different functions", function(){
  var arrayOfData = [1,2,3];
  var expectedResult = 9;
  var handlerOne = function(data){
   return map(data, function(number){
    return number +1;
   });
  }
  var handlerTwo = function(data){
   var result = 0;
   return reduce(data, result, function(result, number){
    return result + number;
   });
  }
  var pipeLine = new PipeLine();

  var pipeLineResult = pipeLine.pipe(handlerOne)
         .pipe(handlerTwo)
         .execute(arrayOfData);

  expect(expectedResult).to.eql(pipeLineResult);       
 });
});

describe("curry function", function(){
  var expectedResult = 10;
  var add = function(a, b, c, d){
   return a + b + c + d;
  }
  var curriedFunction = curry(add);
  beforeEach(function(){});
  it("curry function with all parameters as partial", function(){
   var result = curriedFunction(1)(2)(3)(4); 

   expect(expectedResult).to.eql(result);
  });

  it("curry function with two parameters as partial", function(){
   var result = curriedFunction(1, 2)(3)(4); 
   
   expect(expectedResult).to.eql(result);
  });

  it("curry function with one parameters as partial", function(){
   var result = curriedFunction(1, 2, 3)(4);
   
   expect(expectedResult).to.eql(result);
  });

  it("curry function with parameters as partial in two pairs", function(){
   var result = curriedFunction(1, 2)(3, 4);
   
   expect(expectedResult).to.eql(result);
  });

  it("curry function with parameters as usual", function(){
   var result = curriedFunction(1, 2, 3, 4);
   
   expect(expectedResult).to.eql(result);
  });
 });

Playing with promises in javascript

Reading about callbacks, monads, ... I've tried q library.
Interesting reading about monads and promises, source

This the code.

var fs = require('fs');
var Q = require('q');

function readFile(file){
  var deferred = Q.defer();
  fs.readFile(file, 'utf8', function (err, data) {
    if (err){
   deferred.reject(err);
 } 
    else{
   deferred.resolve(data);
 }
  });
  return deferred.promise;
}

var textFilteContent = readFile('notes.txt');

textFilteContent.then(function(data){
 console.log(data);
}).fail(function(err){
 console.log('error reading the file: ', err);
});

console.log('end');

Lean Code Kata

Yesterday I was in an event at Software Craftsmanship Madrid. It was about lean code. The result of the exercise lives in my repo at Github.com. The code could be refactored. But I am learning that early refactoring could be a wrong decision for the future.