Pattern: Iteration and Applying - applying a callback function to multiple[each] item in a list

pattern_iterationAndApplying.js

// create a function called forEach that iterates over all items in a list and calls a callback for each item
// note: this concept is attached to the array object automatically. this is just to illustrate what is happening under the hood

items = ['one', 'two', 'three'];

//iterator function 1
forEach = function (array, func) { //func = callback function that is passed in (the iterator!)
  for (var i = 0; i < array.length; i++) {
    func(array[i], i); //item in array, and index item in array
  }
}; 

forEach(items, function (item, idx) { //print each index and each item
  console.log(idx = ': ' + item);
}); //output: 0: one, 1: two, 2: three

// iterator function 2 (map function) - transform items
map = func (array, func) {
  var newArray = [];
  var result;
  
  for (var i = 0; i < array.length; i++) {
    result = func(array[i], i);
    newArray.push(result;)
  }
  
  return newArray;
};

newArray = map(items, function(item, idx) {
  return item + '-new';
});

//inspect newArray object //array: ["one-new","two-new","three-new"]