JS Twist

Twist 1 - Callbacks - Solutions

// 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) {
	let newArray = [];
  newArray.forEach(callback)
  for (let i = 0; i < array.length; i++) {
    newArray.push(callback(array[i]));
  }
  return newArray;
}
// console.log(map([1, 2, 3], addTwo));


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


// check below---------------

// let newArray = [];
// let array = [1, 2, 3]
// forEach(array, function(item) {
//   newArray.push(item * 2);
// });
// console.log(newArray);

// see for yourself if your forEach works!

// check above---------------

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

//Extension 1
function mapWith(array, callback) {
  
 	let newArray = [];  
  
	forEach(array, function(item) {
    newArray.push(callback(item));
  });
  
	return newArray;
  
}

// mapWith([1, 2, 3], addTwo);

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

// console.log(reduce([1, 2, 3, 4, 5], function(a, b) { return a + b; }, 0));
//Extension 3
function intersection(arrays) {
  let allArrays = [];
  for (let arr of arguments) {
    allArrays.push(arr);
  }
	// console.log(allArrays);
	return reduce(allArrays, function(resultArr, arr) {
    // forEach(arr, function(num) {
    let wrongs = [];
    for (let j = 0; j < arr.length; j++) {
      for (let i = 0; i < allArrays.length; i++) {
        if (allArrays[i].indexOf(arr[j]) === - 1) {
          wrongs.push(arr[j]);
        }
      }
      if (wrongs.indexOf(arr[j]) === -1 && resultArr.indexOf(arr[j]) === -1) {
        resultArr.push(arr[j])
      }
    };
    return resultArr;
  }, []);
    
}

// 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 reduce(arguments, function (resultArr, arr) {
    for (let i = 0; i < arr.length; i++) {
    	if (resultArr.indexOf(arr[i]) === -1) {
        resultArr.push(arr[i])
      }
    }
    return resultArr;
  }, []);
}

// 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) {
  let obj = {};
  function checker(check1) {
    return callback(check1)
  }
    for (let i = 0; i < array1.length; i++) {
    	if (checker(array1[i]) === array2[i]) {
        obj[array1[i]] = array2[i];
      }
  	}
  
  return obj;
}

// 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) {
	let obj = {};
  	
  function callbacks(value) {
    let array = [];
    for (let i = 0; i < arrCallbacks.length; i++) {
      array.push(arrCallbacks[i](value));
    }
    return array;
  }
  
  for (let i = 0; i < arrVals.length; i++) {
    obj[arrVals[i]] = callbacks(arrVals[i]);
  }
  return obj;
}

// 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 newObject = Object.entries(obj);
  function filter(item) {
    return callback(item);
  }
  for (let i = 0; i < newObject.length; i++) {
      if (newObject[i][1] !== filter(newObject[i][1])) {
        newObject.splice(i, 1)
      }
  }
  
  return newObject;
}

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

//Extension 4

function union(arrays) {
 
	return reduce(arguments, function (resultArr, arr) {
    for (let el of arr) {
    	if (!resultArr.includes(el)) {
        resultArr.push(el)
      }
    }
    return resultArr;
  }, []);
}

includes - реально бомба, забывай про indexOf ;)

//Extension 5

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

убрал checker, так как он просто так существует))

//Extension 6

function multiMap(arrVals, arrCallbacks) {
  const obj = {};
  forEach(arrVals, el => {
    obj[el] = map(arrCallbacks, cb => cb(el))
  });
  return obj;
}

а тут я воспользуюсь тобою созданными инструментами:) (немного функционального программирования)
Так реально намного легче твой код читается, просто надо привыкнуть

//Extension 7

function objectFilter(obj, callback) {
  const newObject = Object.entries(obj);
  for (let i = 0; i < newObject.length; i++) {
      if (newObject[i][1] !== callback(newObject[i][1])) {
        newObject.splice(i, 1)
      }
  }
  
  return newObject;
}

filter - лишняя функция