Functional programming in js

functional-programming.js

function mapForEach(array, fn) {
  var tmpArr = [];
  
  for (var i = 0; i < array.length; i++) {
    tmpArr.push(
      fn(arr[i])
    );
  }
  
  return tmpArr;
}


var arr1 = [1, 2, 3];

var arr2 = mapForEach(arr1, function(item) {
  return item * 3;
});

var arr3 = mapForEach(arr1, function(item) {
  return item > 2;
});

var largerThan = function(limit, item) {
  return item > limit;
};
var arr4 = mapForEach(arr1, largerThan.bind(this, 1));  // passing limit as 1 using .bind()

var largerThanSimplified = function(lim) {
  return function(limit, item) {
    return item > limit;
  }.bind(this, lim);
};
var arr5 = mapForEach(arr1, largerThanSimplified(2));


console.log(arr1);  // [1, 2, 3]
console.log(arr2);  // [3, 6, 9]
console.log(arr3);  // [false, false, true]
console.log(arr4);  // [false, true, true]
console.log(arr5);  // [false, false, true]