fun.js

var data = [0,1,2,3,4,5,6,7,8,9];

function test() {
  var g = window;
  g.result = [];
  for(var i = 0; i < data.length; i++) {
    if(data[i] % 2 === 0) {
      g.result.push(data[i]*2);
    }
  }

  g.sum = 0;
  for(i = 0; i < result.length; i++) {
    g.sum += result[i];
  }
}

var animals = ["dog", "bird", "cat"];

function map(f, arr) {
  var result = [];
  for (var i = 0; i < arr.length; i++) {
    result.push(f(arr[i]));
  }
  return result;
}

function filter(test, arr) {
  var result = [];
  for (var i = 0; i < arr.length; i++) {
    if (test(arr[i])) {
      result.push(arr[i]);
    }
  }
  return result;
}

function reduce(f, init, arr) {
  var acc = init;
  for (var i = 0; i < arr.length; i++) {
    acc = f(acc, arr[i]);
  }
  return acc;
}

function mul2(n) { return n * 2; }
function even(n) { return n % 2 === 0; }
function not(test) { return function(x) { return !test(x); }; }
function sum(a, b) { return a + b; }
// data.filter(even).map(mul2).reduce(sum);

// generic not that accepts many arguments
function negate(test) {
  return function() {
    return !test.apply(null, arguments);
  };
}

// Lazy sequences

function lazyseq(h, f) {
  return {
    head: h,
    tail: f
  };
}

function ints(start) {
  return lazyseq(start, function() { return ints(start+1); });
}

function take(n, seq) {
  if (n === 0) return null;
  return lazyseq(seq.head, function() {
    return take(n - 1, seq.tail());
  });
}

function into_array(seq) {
  var result = [];

  while(seq) {
    result.push(seq.head);
    seq = seq.tail();
  }

  return result;
}

function lmap(f, seq) {
  if (seq === null) return null;
  return lazyseq(f(seq.head), function() {
    return lmap(f, seq.tail());
  });
}

function lfilter(test, seq) {
  if (seq === null) return null;
  if (test(seq.head)) {
    return lazyseq(seq.head, function() { 
      return lfilter(test, seq.tail());
    });
  } else {
    return lfilter(test, seq.tail());
  }
}

function repeat(x) {
  return lazyseq(x, function() {
    return repeat(x);
  });
}

function interleave(seqa, seqb) {
  if (seqa === null) return null;
  if (seqb === null) return null;
  return lazyseq(seqa.head, function() {
    return interleave(seqb, seqa.tail());
  });
}