[INTERVIEW] Coding challenge to test functional programming knowledge and generic JS skills

cc_functional_programming.js

// Remember to overwite the code in CodeShare, JSFiddle, etc. to restore the inital state of the test and to avoid
// showing to candidates the changes made during other interwies

// TASKS:
// 1. Ask to developer to write a foreach function:
//    - The dev should be familiar with .forEach/.each()
//    - The dev should be familiar with the interface of these methods
//    - The dev should be able to implement it (quite easy, see below for the implementation)
// 2. Ask to developer to write a map function:
//    - The dev should be familiar with .map()
//    - The dev should be familiar with the interface of this method
//    - The dev should be able to implement it, (hard, see below for the implementation)


// JUST REFERENCE, DELETE BEFORE INTERVIEWING
function forEach(collection, iterator) {
  // Don't expect them to write this condition, you might ask fot it though
  if (!Array.isArray(collection)) {
    throw new Error('Collection is not Array');
  }
  
  for (let i = 0; i < collection.length; i++) {
    iterator(collection[i], i, collection);
  }
}

// JUST REFERENCE, DELETE BEFORE INTERVIEWING
function map(collection, iterator) {
  const result = [];
  
  forEach(collection, (value, index, collection) => {
  	result.push(iterator(value, index, collection));
  });
  
  return result;
}

Links

CodeShare - JSFiddle