FeM - Javasscript Hard Parts Closure Exercises

closures.js

// Type JavaScript here and click "Run Code" or press Ctrl + s
// console.log('Hello, world!');

// CHALLENGE 1
function createFunction() {
  return function() {
    console.log("hello");
  };
}

// /*** Uncomment these to check your work! ***/
// const function1 = createFunction();
// function1(); // => should console.log('hello');

// CHALLENGE 2
function createFunctionPrinter(input) {
  return function() {
    console.log(input);
  };
}

// /*** Uncomment these to check your work! ***/
// const printSample = createFunctionPrinter('sample');
// printSample(); // => should console.log('sample');
// const printHello = createFunctionPrinter('hello');
// printHello(); // => should console.log('hello');

// CHALLENGE 3
function outer() {
  let counter = 0; // this variable is outside incrementCounter's scope
  function incrementCounter() {
    counter++;
    console.log("counter", counter);
  }
  return incrementCounter;
}

const willCounter = outer();
const jasCounter = outer();

// Uncomment each of these lines one by one.
// Before your do, guess what will be logged from each function call.

// /*** Uncomment these to check your work! ***/
// willCounter();
// willCounter();
// willCounter();

// jasCounter();
// willCounter();

function addByX(x) {
  return function(input) {
    return input + x;
  };
}

// /*** Uncomment these to check your work! ***/
const addByTwo = addByX(2);
console.log();
// addByTwo(1) // => should return 3
// addByTwo(2) // => should return 4
// addByTwo(3); // => should return 5

// const addByThree = addByX(3);
// addByThree(1); // => should return 4
// addByThree(2); // => should return 5

// const addByFour = addByX(4);
// addByFour(4); // => should return 8
// addByFour(5); // => should return 9

// CHALLENGE 4
function once(func) {
  let output;
  return function(input) {
    if (output) return output;
    output = func(input);
    return output;
  };
}

// /*** Uncomment these to check your work! ***/
// const onceFunc = once(addByTwo);
// console.log(onceFunc(4));  // => should log 6
// console.log(onceFunc(10));  // => should log 6
// console.log(onceFunc(9001));  // => should log 6

// CHALLENGE 5
function after(count, func) {
  let callsCount = 0;
  return function() {
    callsCount++;
    if (callsCount === count) {
      return func();
    }
  };
}

// /*** Uncomment these to check your work! ***/
// const called = function() { console.log('hello') };
// const afterCalled = after(3, called);
// afterCalled(); // => nothing is printed
// afterCalled(); // => nothing is printed
// afterCalled(); // => 'hello' is printed

// CHALLENGE 6
function delay(func, wait) {
  return function() {
    setTimeout(func, wait);
  };
}

// const delayedFunc = delay(() => console.log('Oops!'), 3000);
// delayedFunc();

// CHALLENGE 7
function rollCall(names) {
  let index = 0;
  return function() {
    console.log(index);
    if (index > names.length - 1) {
      return console.log("Everyone accounted for");
    }
    console.log(names[index]);
    index++;
  };
}

// /*** Uncomment these to check your work! ***/
// const rollCaller = rollCall(['Victoria', 'Juan', 'Ruth'])
// rollCaller() // => should log 'Victoria'
// rollCaller() // => should log 'Juan'
// rollCaller() // => should log 'Ruth'
// rollCaller() // => should log 'Everyone accounted for'

// CHALLENGE 8
function saveOutput(func, magicWord) {
  let store = {};
  return function(input) {
    if (input === magicWord) return store;

    const result = func(input);
    store[input] = result;
    return result;
  };
}

// /*** Uncomment these to check your work! ***/
// const multiplyBy2 = function(num) { return num * 2; };
// const multBy2AndLog = saveOutput(multiplyBy2, 'boo');
// console.log(multBy2AndLog(2)); // => should log 4
// console.log(multBy2AndLog(9)); // => should log 18
// console.log(multBy2AndLog('boo')); // => should log { 2: 4, 9: 18 }

// CHALLENGE 9
function cycleIterator(array) {
  let index = 0;

  return function() {
    const item = array[index];
    console.log(index);

    if (index === array.length - 1) {
      index = 0;
    } else {
      index++;
    }

    return item;
  };
}

// /*** Uncomment these to check your work! ***/
// const threeDayWeekend = ['Fri', 'Sat', 'Sun'];
// const getDay = cycleIterator(threeDayWeekend);
// console.log(getDay()); // => should log 'Fri'
// console.log(getDay()); // => should log 'Sat'
// console.log(getDay()); // => should log 'Sun'
// console.log(getDay()); // => should log 'Fri'

// CHALLENGE 10
function defineFirstArg(func, arg) {
  return function(input) {
    return func(arg, input);
  };
}

// /*** Uncomment these to check your work! ***/
// const subtract = function(big, small) { return big - small; };
// const subFrom20 = defineFirstArg(subtract, 20);
// console.log(subFrom20(5)); // => should log 15

// CHALLENGE 11
function dateStamp(func) {
  return function(...args) {
    return {
      date: Date.now(),
      output: func(...args)
    };
  };
}

// /*** Uncomment these to check your work! ***/
// const stampedMultBy2 = dateStamp(n => n * 2);
// console.log(stampedMultBy2(4)); // => should log { date: (today's date), output: 8 }
// console.log(stampedMultBy2(6)); // => should log { date: (today's date), output: 12 }

// CHALLENGE 12
function censor() {
  let replaces = [];

  return function(str1, str2) {
    if (str2) {
      replaces.push({ from: str1, to: str2 });
    } else {
      return replaces.reduce((text, currReplace) => {
        return text.replace(currReplace.from, currReplace.to);
      }, str1);
    }
  };
}

// /*** Uncomment these to check your work! ***/
// const changeScene = censor();
// changeScene('dogs', 'cats');
// changeScene('quick', 'slow');
// console.log(changeScene('The quick, brown fox jumps over the lazy dogs.')); // => should log 'The slow, brown fox jumps over the lazy cats.'

// CHALLENGE 13
function createSecretHolder(secret) {
  let _secret = secret;

  return {
    getSecret: () => {
      return _secret;
    },
    setSecret: () => {
      _secret = secret;
    }
  };
}

// /*** Uncomment these to check your work! ***/
// let obj = createSecretHolder(5)
// console.log(

// obj.getSecret(), // => returns 5
// obj.setSecret(2),
// obj.getSecret() // => returns 2
// )

// CHALLENGE 14
function callTimes() {
  let callsCount = 0;
  return function() {
    console.log(++callsCount);
  };
}

// /*** Uncomment these to check your work! ***/
// let myNewFunc1 = callTimes();
// let myNewFunc2 = callTimes();
// myNewFunc1(); // => 1
// myNewFunc1(); // => 2
// myNewFunc2(); // => 1
// myNewFunc2(); // => 2

// CHALLENGE 15
function russianRoulette(num) {
  let callsCount = 0;
  let finished = false;
  return function() {
    if (finished) return "reload to play again";

    callsCount++;
    if (callsCount === num) {
      finished = true;
      return "bang";
    }

    return "click";
  };
}

// /*** Uncomment these to check your work! ***/
// const play = russianRoulette(3);
// console.log(play()); // => should log 'click'
// console.log(play()); // => should log 'click'
// console.log(play()); // => should log 'bang'
// console.log(play()); // => should log 'reload to play again'
// console.log(play()); // => should log 'reload to play again'

// CHALLENGE 16
function average() {
  let average = 0;
  let numbers = [];

  const calculateAverage = number => {
    if (!numbers.length) return 0;
    const sum = numbers.reduce((accum, currNum) => accum + currNum, 0);
    return sum / numbers.length;
  };

  return function(number) {
    if (!number) return calculateAverage(number);
    numbers.push(number);
    return calculateAverage(number);
  };
}

// /*** Uncomment these to check your work! ***/
const avgSoFar = average();
// console.log(avgSoFar()); // => should log 0
// console.log(avgSoFar(4)); // => should log 4
// console.log(avgSoFar(8)); // => should log 6
// console.log(avgSoFar()); // => should log 6
// console.log(avgSoFar(12)); // => should log 8
// console.log(avgSoFar()); // => should log 8

// CHALLENGE 17
function makeFuncTester(arrOfTests) {
  return function(callback) {
    return arrOfTests.every(test => {
      const [first, second] = test;
      return callback(first) === second;
    });
  };
}

// /*** Uncomment these to check your work! ***/
// const capLastTestCases = [];
// capLastTestCases.push(['hello', 'hellO']);
// capLastTestCases.push(['goodbye', 'goodbyE']);
// capLastTestCases.push(['howdy', 'howdY']);
// const shouldCapitalizeLast = makeFuncTester(capLastTestCases);
// const capLastAttempt1 = str => str.toUpperCase();
// const capLastAttempt2 = str => str.slice(0, -1) + str.slice(-1).toUpperCase();
// console.log(shouldCapitalizeLast(capLastAttempt1)); // => should log false
// console.log(shouldCapitalizeLast(capLastAttempt2)); // => should log true

// CHALLENGE 18
function makeHistory(limit) {
  let history = [];

  return function(str) {
    if (str === "undo") {
      if (!history.length) {
        return "nothing to undo";
      }
      const strToUndo = history[history.length - 1];
      history = history.slice(0, -1);
      return `${strToUndo} undone`;
    }

    history = [...history, str].slice(history.length === limit ? limit - 1 : 0);
    return `${str} done`;
  };
}

// /*** Uncomment these to check your work! ***/
// const myActions = makeHistory(2);
// console.log(myActions('jump')); // => should log 'jump done'
// console.log(myActions('undo')); // => should log 'jump undone'
// console.log(myActions('walk')); // => should log 'walk done'
// console.log(myActions('code')); // => should log 'code done'
// console.log(myActions('pose')); // => should log 'pose done'
// console.log(myActions('undo')); // => should log 'pose undone'
// console.log(myActions('undo')); // => should log 'code undone'
// console.log(myActions('undo')); // => should log 'nothing to undo'

// CHALLENGE 19
function blackjack(array) {
  let index = 0;
  return function dealer(num1, num2) {
    let hasLostGame = false;
    let currentSum = 0;
    return function player() {
      if (hasLostGame) {
        return "you are done!";
      }

      if (currentSum === 0) {
        currentSum = num1 + num2;
        return currentSum;
      }

      currentSum += array[index++];

      if (currentSum > 21) {
        hasLostGame = true;
        return "bust";
      }

      return currentSum;
    };
  };
}

// /*** Uncomment these to check your work! ***/

// /*** DEALER ***/
// const deal = blackjack([2, 6, 1, 7, 11, 4, 6, 3, 9, 8, 9, 3, 10, 4, 5, 3, 7, 4, 9, 6, 10, 11]);

// /*** PLAYER 1 ***/
// const i_like_to_live_dangerously = deal(4, 5);
// console.log(i_like_to_live_dangerously()); // => should log 9
// console.log(i_like_to_live_dangerously()); // => should log 11
// console.log(i_like_to_live_dangerously()); // => should log 17
// console.log(i_like_to_live_dangerously()); // => should log 18
// console.log(i_like_to_live_dangerously()); // => should log 'bust'
// console.log(i_like_to_live_dangerously()); // => should log 'you are done!'
// console.log(i_like_to_live_dangerously()); // => should log 'you are done!'

// // /*** BELOW LINES ARE FOR THE BONUS ***/

// // /*** PLAYER 2 ***/
// const i_TOO_like_to_live_dangerously = deal(2, 2);
// console.log(i_TOO_like_to_live_dangerously()); // => should log 4
// console.log(i_TOO_like_to_live_dangerously()); // => should log 15
// console.log(i_TOO_like_to_live_dangerously()); // => should log 19
// console.log(i_TOO_like_to_live_dangerously()); // => should log 'bust'
// console.log(i_TOO_like_to_live_dangerously()); // => should log 'you are done!
// console.log(i_TOO_like_to_live_dangerously()); // => should log 'you are done!

// // /*** PLAYER 3 ***/
// const i_ALSO_like_to_live_dangerously = deal(3, 7);
// console.log(i_ALSO_like_to_live_dangerously()); // => should log 10
// console.log(i_ALSO_like_to_live_dangerously()); // => should log 13
// console.log(i_ALSO_like_to_live_dangerously()); // => should log 'bust'
// console.log(i_ALSO_like_to_live_dangerously()); // => should log 'you are done!
// console.log(i_ALSO_like_to_live_dangerously()); // => should log 'you are done!