callbacks.js

// Challenge 1
function addTwo(num) {
  return num + 2;
}

// To check if you've completed it, uncomment these console.logs!
// console.log(addTwo(3));
// console.log(addTwo(10));


// Challenge 2
function addS(word) {
  return word + 's';
}

// uncomment these to check your work
// console.log(addS('pizza'));
// console.log(addS('bagel'));


// Challenge 3
function map(array, callback) {
  const mappedArray = [];
  for (let i = 0; i < array.length; i++) {
    mappedArray.push(callback(array[i]));
  }
  return mappedArray;
}

// console.log(map([1, 2, 3], addTwo));


// Challenge 4
function forEach(array, callback) {
  for (let i = 0; i < array.length; i++) {
    callback(array[i]);
  }
}

// see for yourself if your forEach works!


//--------------------------------------------------
// Extension
//--------------------------------------------------

//Extension 1
function mapWith(array, callback) {
  const mappedArray = [];
  forEach(array, el => mappedArray.push(callback(el)));
  return mappedArray;
}


//Extension 2
function reduce(array, callback, initialValue) {
  let acc = initialValue;
  for (let i = 0; i < array.length; i++) {
    acc = callback(acc, array[i]);
  }
  return acc;
}


//Extension 3
function intersection(arrays) {
  return arrays.reduce((acc, curr) => {
    return curr.filter(el => acc.includes(el));
  });
}

// console.log(intersection([[5, 10, 15, 20], [15, 88, 1, 5, 7], [1, 10, 15, 5, 20]]));
// should log: [5, 15]

//Extension 4
function union(arrays) {
  return arrays.reduce((acc, curr) => {
    const newElements = curr.filter(el => !acc.includes(el));
    return acc.concat(newElements);
  });
}

// console.log(union([[5, 10, 15], [15, 88, 1, 5, 7], [100, 15, 10, 1, 5]]));
// should log: [5, 10, 15, 88, 1, 7, 100]

//Extension 5
function objOfMatches(array1, array2, callback) {
  const matchObj = {};
  for (let i = 0; i < array1.length; i++) {
    if (callback(array1[i]) === array2[i]) {
      matchObj[array1[i]] = array2[i];
    }
  }
  return matchObj;
}

// console.log(objOfMatches(['hi', 'howdy', 'bye', 'later', 'hello'], ['HI', 'Howdy', 'BYE', 'LATER', 'hello'], function(str) { return str.toUpperCase(); }));
// should log: { hi: 'HI', bye: 'BYE', later: 'LATER' }

//Extension 6
function multiMap(arrVals, arrCallbacks) {
  const multiMapObj = {};
  for (let i = 0; i < arrVals.length; i++) {
    multiMapObj[arrVals[i]] = [];
    for (let j = 0; j < arrCallbacks.length; j++) {
      multiMapObj[arrVals[i]].push(arrCallbacks[j](arrVals[i]));      
    }
  }
  return multiMapObj;
}

// console.log(multiMap(['catfood', 'glue', 'beer'], [function(str) { return str.toUpperCase(); }, function(str) { return str[0].toUpperCase() + str.slice(1).toLowerCase(); }, function(str) { return str + str; }]));
// should log: { catfood: ['CATFOOD', 'Catfood', 'catfoodcatfood'], glue: ['GLUE', 'Glue', 'glueglue'], beer: ['BEER', 'Beer', 'beerbeer'] }


//Extension 7
function objectFilter(obj, callback) {
  const newObj = {};
  for (let key in obj) {
    if (callback(key) === obj[key]) {
      newObj[key] = callback(key);
    }
  }
  return newObj;
}

// const cities = {
//   London: 'LONDON',
//   LA: 'Los Angeles',
//   Paris: 'PARIS',
// };
// console.log(objectFilter(cities, city => city.toUpperCase())) // Should log { London: 'LONDON', Paris: 'PARIS'}