• Numbers

Write a function named totalEggs that takes two arguments, a number of hard-boiled eggs and a number of soft-boiled eggs you want to make and returns the total number of eggs you need.

• Numbers

Write a function named chocolatesPerPerson that takes two arguments, a number of chocolates and a number of people. Return the largest whole number of chocolates you can give to each person if everyone gets the same amount. For instance, chocolatesPerPerson(13, 5) should return 2.

• Numbers

Write a function named extraChocolates that takes two arguments, a number of chocolates and a number of people. Return the number of chocolates that are left over after distributing the chocolates evenly to all the people. For instance, For instance, extraChocolates(13, 5) should return 3.

• Numbers

Write a function named leftOut that takes two arguments, a number of chocolates and a number of people. Return the number of people who won’t get a chocolate if you try to distribute them evenly and there are more people than chocolates. However, if there are enough chocolates for everyone to get at least one the function should return 0. For example, leftOut(10, 13) should return 3 but leftOut(13, 10) should return 0.

• Numbers

Write a function named probabilityAllHeads that takes a single argument specifying the number of times a coin will be flipped and returns the probability (a number between 0 and 1, inclusive) of getting all heads. For instance probabilityAllHeads(1) should return 0.5 since the chance of getting heads on one toss is 1/2. And probabilityAllHeads(2) should return 0.25 since the chance of two independent outcomes—such as getting a head on each of two flips of a coin—both occuring is the product of their probabilities, in this case 0.5 × 0.5 = 0.25. For reference probabilityAllHeads(10) should return 0.0009765625.

• Numbers

Write a function named futureHour that takes two arguments, the current hour on a 24-hour clock, i.e. a number from 0-23 inclusive, and a positive number of hours in the the future that an event will occur. Return the hour it will be when the event occurs. For example, futureHour(9, 4) should return 13 since four hours after 9 it will be hour 13. Note that the number of hours can be arbitrarily large: futureHour(9, 28) would also return 13 since the event would occur at hour 13 the next day.

• Numbers

Write a function named presentsBudget that takes two arguments, the number of friends you are buying presents for and the average price of present you plan to buy, and returns the total amount of money you expect to spend. For instance presentsBudget(6, 15), i.e. six friends on whom you want to spend an average of fifteen dollars, should return 90.

• Numbers

Write a function named perPresent that takes two arguments, the total amount of money you have budgeted for buying presents and the number of presents you need to buy, and returns the average amount you can spend per present. Thus perPresent(90, 6) should return 15 since with a budget of ninety dollars and six presents to buy, you can spend an average of fifteen dollars per present.

• Numbers

Write a function named wrapingCombos that takes three arguments, the number of kinds of wrapping paper you have, the number of kinds of ribbions you have, and the number of kinds of decorative bows you have. Return the number of different combinations of paper, ribbon, and bow you could produce, using one kind of paper, one kind of ribbon, and one bow to wrap a present. For example, with just two kinds of paper, three kinds of ribbon, and five different bows there are thirty combinatons: for the two kinds of paper you can choose any of the three ribbons, giving six paper/ribbon combinations. And each of those combinations can be topped with one of five different bows, giving thirty total combinations. Thus wrappingCombos(2, 3, 5) should return 30.

• Numbers

Write a function named biggestNumber that takes a single argument representing a number of digits and returns the largest number that can be written in our ordinary decimal (base-10) number system using that many digits. For instance:

• biggestNumber(1) should return 9
• biggestNumber(2) should return 99
• biggestNumber(3) should return 999

Hint: As a starting point, you might want to think about the numbers one bigger than these numbers and how you could express them in terms of the desired number of digits.

• Numbers

Write a function named itemsLeftOver that takes two arguments, a number of people and a number of items, and returns the number of items that will be left over after you give each person the maximum number of items you can while giving everyone the same number of items.

• Numbers

Write a function named areaOfCircle that takes one argument, the radius of a circle, and returns the area of the circle. The formula for the area of a circle with radius r is πr². In Javascript you can use Math.PI to get a good approximation of π.

• Numbers

Write a function named volumeOfCube that takes a single argument specifying the length of one edge of a cube, and returns the volume of the cube.

• Numbers

Write a function named populationGrowth that takes two numeric arguments, the current size of a population and a growth rate expressed as a fraction the population will grow in a day. The function should return the amount by which the population will grow in one day. For example, if the population was initially 100 and the growth rate was 0.25, it would grow by 25 members.

• Numbers

Write a function named earnedRunAverage that takes two arguments, the number of “earned runs” a baseball pitcher has given up and the number of innings that pitcher has pitched. The function should return the pitcher’s Earned Run Average (ERA) which is defined as the average number of earned runs per inning pitched multiplied by 9.

• Numbers

Write a function named valueOfJewels that takes four arguments, a number of diamonds, a number of emeralds, the value of one diamond in gold pieces, and the value of one emerald in gold pieces. The function should return the value in gold pieces of the given number of diamonds and emeralds. In other words multiply the number of each type of jewel by the value of that kind of jewel and sum the products.

• Numbers

Write a function named payWithOvertime that takes three numeric arguments, a number of hours someone worked, their normal hourly rate, and their overtime rate. The function should return how much they are paid for the hours worked assuming that they are paid their normal rate for the first eight hours and their overtime rate for any hours beyond that.

• Numbers

Write a function named firstClassPostage that takes one argument, the weight in ounces of a letter. It should return the postage needed, in cents, to mail the letter given that anything up the first ounce costs 60 cents and each additional ounce, or fractional ounce, costs 24 cents. A function that will be useful is Math.ceil which returns the smallest integer greater than or equal to its single argument. For instance, Math.ceil(2.3) is 3.

• Numbers

Write a function named weightOnJupiter that takes a single argument, the weight of a person in kilograms on Earth, and returns the weight of that same person on Jupiter.

Note that weights on other planets are computed by multiplying the Earth weight by the ratio of the other planet’s gravity to Earth’s gravity. For instance, if there was a planet whose gravity was exactly twice Earth’s, then someone would weight exactly twice as much on that planet as on Earth. Two useful constants defined in the starter code for you are JUPITER_GRAVITY and EARTH_GRAVITY

• Numbers

Write a function named gravity that takes three numeric arguments, the first two are the masses of two bodies (such as planets) and the third is the distance between the two objects. It should return the gravitational force attracting the two bodies which is computed as the product of the bodies’ masses divided by the square of the distance between them, all multiplied by the universal gravitational constant which is defined for you in the starter code as the constant G.

• Numbers

Write a function named averageWeight that takes two arguments, the total weight of a number of items and the number of items, and returns the average weight of an item. E.g. if the total weight is 1,000 and there are 20 items, the average weight is 50.

• Numbers

Write a function named hypotenuse that takes two arguments representing the lengths of the two legs of a right triangle and returns the length of the hypotenuse. Recall the Pythagorean theorem that tells us that c² = a² + b² where a and b are the lengths of the two legs of a right triangle and c is the length of the hypotenuse.

• Numbers

Write a function named maxRadius that takes two arguments, the first being the width and the second being the height of a drawing area. It should return the radius of the largest circle that can be drawn in the drawing area.

• Numbers

Write a function named numCircles that takes two arguments, the radius of a circle and the width of a drawing area, and returns the largest integer number of non-overlapping circles of the given radius that can be drawn in a line across the drawing area..

• Numbers

Write a function named offset that takes two arguments, the width, in pixels, of a drawing area and the width of a figure (guaranteed to be less than the total width, also in pixels) and which returns the number of pixels from the left side of the drawing to shift the figure to be horizontally centered in the drawing area.

• Booleans

The BHS fire alarms go off if a fire alarm is pulled, if smoke is detected, or if there is a planned fire drill. Write a function named fireAlarm that takes three arguments and returns a boolean value indicating whether the fire alarm should go off.

The values of the arguments will be booleans indicating, in order, whether a fire alarm was pulled, whether smoke was detected, and whether there is a planned fire drill.

• Booleans

There are three criteria for a person to be eligible to be elected president of the United States: they must be at least 35 years old, they must be a natural born citizen, and they must have lived in the US for at least fourteen years. A person must meet all these criteria to be eligible.

Write a function named canBePresident that takes three arguments, and returns true if a person can be president. The first argument is the persons age in years; the second, a boolean indicating whether or not they are a natural born citizen; and the third, the number of years they’ve lived in the US.

• Booleans

On Twitter, a user should see a tweet if they follow the person who tweeted it or if they follow a person who retweeted it. However they should never see a tweet from someone they have blocked.

Write a function named willSeeTweet that returns a boolean indicating whether a user should see a given tweet according to the values of its three boolean arguments. The first says whether they follow the tweeter; the second, whether they follow someone who retweeted the tweet; and the third, whether they have blocked the original tweeter.

• Booleans

Write a function named needHeavyCoat that takes two boolean arguments, one that is true if a person is going outside and the other that is true if they are somewhere cold, and returns a boolean indicating whether they need a heavy coat which they only need if they are going outside somewhere cold.

• Booleans

Write a function named needSunscreen that takes two boolean arguments, one that is true if someone is going to the beach and the other that is true if they are going skiing, and returns a boolean indicating whether they need to wear sunscreen which they need to do both at the beach and on the ski slopes.

• Booleans

Write a function named needMittens that takes two boolean arguments, one which is true if a person is going outside and the other which is true if they are somewhere warm, and returns a boolean indicating whether they need to wear mittens which they need if they are going outside somewhere that isn’t warm.

• Booleans

Write a function named isVenomous that returns a boolean indicating whether a snake on the island of Booleana is venomous based on two boolean arguments, one which is true if the snake is striped and the other of which is true if the snake has a blue head. All striped snakes on Booleana are venomous as are all of the unstriped snakes on the island except the blue-headed Blooby Snake.

• Booleans

Write a function named isMagicNumber that takes a single numeric argument and returns true if the number is one of the two magic numbers, 42 or 17. (For 10,000,000 extra credit points, include a comment about why you think 42 and 17 are magic numbers.)

• Booleans

Write a function named canSleepIn that takes two boolean arguments, the first saying whether it's a weekday and the second saying whether you're on vacation, and returns true if you are allowed to sleep in and false otherwise. The rules are you can always sleep in when you're on vacation and you can also sleep in on weekends.

• Booleans

Write a function named canGoToProm which takes three boolean arguments describing a person. The first specifies if they are a senior, the second specifies if they were invited to prom by a senior, and the third specifies if they are on the prom exclusion list. The function should return a boolean indicating whether or not the person is eligible to go to prom. The rules are seniors and people invited by seniors are eligible unless they are on the exclusion list.

• Booleans

Write a function named getsSpeedingTicket that takes two arguments, a number indicating the speed in miles per hour that you were driving and a boolean indicating whether the cop who pulled you over is grouchy. Return a boolean value indicating whether you will get a ticket given that a grouchy cop will give you a ticket if you are going over 65 while a non-grouchy cop will only give you a ticket if you're going over 70 mph.

• Booleans
• Numbers

Write a function named evenGreaterThanZero that takes a single numeric argument and returns a boolean indicating whether the number is an even number greater than zero.

• Booleans
• Numbers

The rules for leap years are more complex than you may know. The basic rule is that all years evenly divisible by 4 (i.e. year % 4 === 0) are leap years. However, years evenly divisible by 100 are not leap years unless they are evenly divisible by 400. Thus 2004 was a leap year by the normal rule but 2100 will not be because it’s divisible by 100. But 2000 was because although it was divisible by 100 it was also divisible by 400.

Write a function named isLeapYear that takes a single argument of a year number and returns a boolean indicating whether or not it is a leap year.

• Booleans
• Numbers

Write a function named okaySpeed that takes two numeric arguments, one indicating the posted speed limit in miles per hour and the other the speed a car is going, also in miles per hour. It should return true if and only if the speed is no more than ten mph below the posted limit and no more than ten mph above the posted limit.

• Booleans
• Numbers

Write a function named twiceAsExpensive that takes two numeric arguments, each indicating the price of an item you are considering buying. The function should return true if and only if the first item costs more than twice as much as the second item.

• Booleans
• Numbers

Write a function named winningRecord that takes three numeric arguments, a team’s number of wins, losses, and ties. It should return true if the team has a winning record, meaning it has won more than half of the games it has played.

• Booleans
• Numbers

Write a function named aFartherThanB that takes three arguments, all numbers and returns a boolean indicating whether the first argument is farther away (on the number line) from the third argument than the second argument. I.e. if we call the arguments a, b, and c, return true if a is farther away from c than b is.

• Strings

Write a function named firstFewEveryOther that takes a single string argument that is at least five characters long and returns a string consisting of just the first, third, and fifth characters of the argument string. E.g. called with 'foobar' it should return 'foa'.

• Strings

Write a function named firstHalf that takes a single string argument and returns the first half of the string. (If the string has an odd number of characters it doesn't matter whether or not you include the extra character.) For instance the first half of 'foobar' is 'foo' but if the argument was 'fooquux' then either 'foo' or 'fooq' would be acceptable return values.

• Strings

Write a function named secondHalf that takes a single string argument and returns the second half of the string. (If the string has an odd number of characters it doesn't matter whether or not you include the extra character.) For instance the second half of 'foobar' is 'bar' but if the argument was 'fooquux' then either 'quux' or 'uux' would be acceptable return values. For maximum style points write this function and firstHalf so that firstHalf(s) + secondHalf(s) gives you back s.

• Strings

Write a function named swapFrontAndBack that takes a single string argument and returns a string consisting of the second half of the original string followed by the first half. If the string is an odd number of characters it doesn’t matter whether the extra character goes with the front or the back.

• Strings

Write a function named upDown that takes a single string argument and returns a string consisting of the original string all in upper case concatenated (“smooshed together”) with the string all in lower case. E.g. called with 'foo' it should return 'FOOfoo'.

• Strings

Write a function named upDownLastCharacter that takes a single string argument that is at least one character long and returns a string consisting of two characters, the uppercase version of the last character of the argument string and the lowercase version of that same character. E.g. called with 'foo' it should return 'Oo'.

• Strings

Write a function named firstAndLast that takes a single string argument (which will be at least two characters long) and returns a string consisting of just the first and last characters of the string.

• Strings

As you should recall from the Pig Latin assignment, the rules of simple Pig Latin say that a word is translated into Pig Latin by taking everything up to (but not including) the first vowel and moving it to the end of word and then adding “ay” to the end.

Write a function named simplePigLatin that takes two arguments, a string containing a single word and a number indicating the index of the first vowel in the word, and returns the word translated into Pig Latin.

• Strings

Write a function named randomCharacter that takes a single string argument and returns a random character from the string. For this function you will need to use the rand function defined at the top of the starter code.

• Strings

Write a function named randomCharacterUpDown that takes a single string argument and returns a string consisting of a single random character repeated twice, once in upper case and then in lower case. For this function you will need to use the rand function defined at the top of the starter code.

• Strings

Write a function named isAllUpperCase that takes a single string argument and returns a boolean indicating whether the string is all upper case.

• Strings

Write a function named sameIgnoringCase that takes two string arguments and returns a boolean indicating whether they are the same string if you ignore case differences.

• Strings

Write a function named firstName that takes a single string argument which will consist of a full name in the form first name, a space, and the last name and returns a string containing just the first name. You will probably want to use the indexOf method.

• Strings

Write a function named lastName that takes a single string argument which will consist of a full name in the form first name, a space, and the last name and returns a string containing just the last name. You will probably want to use the indexOf method.

• Strings

Write a function named initials that takes a single string argument which will consist of a full name in the form first name, a space, and the last name and returns a string containing the person's initials, i.e. the first letter of their first name followed by the first letter of their last name. You will probably want to use the indexOf method.

• Strings

Write a function named upToX that takes a single string argument and returns a string consisting of the characters of the original string up to but not including the first 'x'. For instance upToX('quixotic') should return 'qui'.

• Strings

Write a function named charactersAround that takes two arguments, a string and an index into the string and returns a string consisting of two characters, the one immediately before the character at the given index and one and the one immediately after the character at the given index. You can assume that those characters exist, i.e. the index is not at the beginning or end of the string. For instance charactersAround('programming', 4) should return 'ga'.

• Strings

Write a function named middle that takes a single string argument and returns a sting consisting of the the middle of the argument, defined as the original string with the first and last quarter removed. You can assume the number of characters in the string is a multiple of four. For instance middle('abcdefgh') should return 'cdef'.

• Strings

Write a function named pair that takes two string arguments and returns a single string consisting of the two arguments separated by the word and. For instance pair('peanut butter', 'jelly') should return peanut butter and jelly.

• Strings

Write a function named containsX that takes a single string argument and returns true if it contains an 'x' and false if it does not. For instance containsX('flexible') should return true and containsX('smooth') should return false.

• Strings

Write a function named slug that takes three string arguments and returns a “slug” consisting of the three strings joined together with hyphens and all in lower case. For instance slug('Foo', 'Bar', 'BAZ') would return 'foo-bar-baz'.

• Strings

Write a function named capitalize that takes a single string argument and returns a string with the same characters but with the first character in upper case and all remaining characters in lower case. For instance capitalize('programming') should return 'Programming'.

• Strings

Write a function named capitalizeName that takes a single string consisting of a first and last name separated by a space and returns a string with the first and last name separated by a space but capitalized using the capitalize function you just wrote. For instance capitalizeName('fred flintstone') should return 'Fred Flintstone'. Note: you must use capitalize in this function to get full credit.

• Strings
• Booleans
• Numbers

Write a function named moreThanTwiceAsLong that takes two string arguments and returns a boolean indicating whether the first string contains more than twice as many characters as the second string.

• Control constructs

Write a function named yesIfEven that takes a single argument which will be a number and returns the string 'yes' if the argument is even and 'no' otherwise.

• Control constructs

Write a function named logIfOk that takes a single argument that can be passed to the function isOk provided in the starter code to get a boolean indicating whether the value is “okay”. If the value is okay according to isOk you should call the provided log function, passing the value so it can be logged. Note: you do not need to write isOk or log but you can adapt the simple implementations in the starter code if you’d like, to test your code.

• Control constructs

Write a function named firstOk that takes a numeric argument and returns the first integer greater than or equal to zero and less than the argument that is okay according to the isOk function. If none of the numbers in the range are okay, it should return undefined.

• Control constructs

Write a function named timeToLeet that repeatedly generates random numbers with the provided random10k() function and returns the number of numbers generated that were not leet, according to the provided isLeet function, before a leet number was generated. (Thus if the very first number generated is leet, it should return 0. If the 101st number generated was leet, then it should return 100.)

• Control constructs

Write a function named classify that takes an arbitrary value as its single argument and calls one of the provided functions recordOk or recordNotOk with the value, the former if the value is okay according isOk and the latter otherwise.

• Control constructs

Write a function named threewayClassify that takes an arbitrary value as its single argument and calls one of the three provided functions recordOk, recordMeh, or recordNotOkwith the value. It should call recordOk if the value is okay according to isOk, recordMeh if the value is meh according to isMeh, and recordNotOk otherwise.

• Control constructs

Write a function named sumOfSquares that takes a single numeric argument and returns the sum of the squares of the positive integers less than the argument. For instance sumOfSquares(10) should return 285.

• Control constructs

Write a function named pairs that takes a single numeric argument and calls the provided pair function with every possible pair of numbers made up of two numbers each in the range from 1 to the argument. For instance, pairs(3) would result in calls to pair with the pairs (1, 1), (1, 2), (2, 1), and (2, 2). Note that order matters so (1, 2) and (2, 1) are different pairs. Also note: pair takes two arguments so you just need to pass the two numbers; you do not need to do anything else to create a pair.

• Control constructs
• Numbers

Write a function named timesTable that takes a single number as its argument and emits a times table of all the products from 1 × 1 to n × n. Use the emit function defined in the starter code to actually emit the different values. It takes three arguments, the two numbers being multiplied and their product, and prints them out nicely; you just need to call it once for each pair of arguments. N.B. that order matters so, assuming you are emitting a times table that includes 2 × 3 you need to call both emit(2, 3, 6) and emit(3, 2, 6).

• Control constructs
• Numbers

Write a function named sumSquares that takes a single number argument and returns the sum of the squares of all the positive integers less than the argument. For instance given the argument 4 it should return 14, i.e. 1² + 2² + 3², i.e. 1 + 4 + 9.

• Control constructs
• Strings
• Booleans
• Numbers

Write a function named countXs that takes a single string argument and returns the number of 'x' characters that occur in the string.

• Arrays

Write a function named makeRow that takes no arguments and returns a new three-element array where each element is the empty string, ''.

• Arrays

Write a function named makeBoard that takes no arguments and returns a 3x3 array. That is, it should return an array containing three elements, each of which is a new array containing three elements. The elements of the inner arrays should all be the empty string, ''. In other words, the inner arrays are rows such as are returned by the makeRow function you just wrote, which you are free to use here if you want.

• Arrays
• Booleans

Write a function named allTheSame that takes an array of three elements and returns true if all three elements are === to each other and false otherwise. For instance, allTheSame(['X', 'X', 'X']) should return true.

• Arrays
• Control constructs

Write a function named extractColumn that takes a 3x3 array like the ones returned by makeBoard and an index from 0 to 2, inclusive, and returns a three-element array containing the values in the column specified by the index, assuming the inner arrays represent rows. For instance if board is the array:

   [
     ['X', '', ''],
     ['O', '', ''],
     ['', 'X', '']
   ]

then extractColumn(board, 0) should return ['X', 'O', '']

• Arrays
• Control constructs
• Numbers

Write a function named fillTimesTable that takes a single n-by-n 2D array as an argument. That is, the argument will be an array with n elements each of which is an array of n elements. The inner arrays will initially be filled with zeros. The function should replace each zero with the products from 1 × 1 at table[0][0] and n × n at table[n - 1][n - 1] and return undefined (Note, n itself is not an argument to the function.)

For instance, if called with the empty table:

[[0 , 0, 0], [0, 0, 0], [0, 0, 0]]

it should leave the table in this state:

[[1, 2, 3], [2, 4, 6], [3, 6, 9]]

• Arrays
• Control constructs
• Numbers

Write a function sums that takes a single number, n and returns an array with n + 1 numbers in it such that each element of the array is the sum of the index of that element and the preceeding indices. (The zeroth element should have the value 0.) For example sums(5) should return [0, 1, 3, 6, 10, 15]. The third item, 3 is 3 because it's at index 2 + the preceeding value of 1.

• Arrays
• Control constructs

Write a function rule110 that takes an array of arbitrary length containing only 0s and 1s as its argument and returns a new array of the same length filled according to the following somewhat complicated rules:

For each index, i, the value at i in the new array is determined by the three values in the original array at i - 1 (the left value), at i (the center value), and at i + 1 (the right value). When i is 0 use 0 for the left value and when i is the last index in the array, use 0 for the right value.

The ith value of the result array will be 0 in three cases: when the left, center, and right values are all 0 or the two cases when the left value is 1 and the center and right values are the same, i.e. both 0s or both 1s. In all other cases, the ith element in the result is 1.

• Objects

Write a function named isSamePoint that takes two point objects as arguments, each with x and y properties, and returns a boolean indicating whether the two objects represent the same x, y coordinate.

• Objects
• Numbers

Write a function named area that takes a single argument which will be an object with width and height properties representing the dimensions of a rectangle and returns the area of the rectangle as a number.

• Objects
• Numbers

Write a function named totalWithTip that takes two arguments, an object with a property subtotal and a number between 0 and 1.0 representing the percentage tip, e.g. 20% tip would be 0.2. Return a new object that has three properties, subtotal with the same value as the argument object, tip which is the tip computed from the subtotal and the given percentage, and total which is the total with the tip.

• Objects
• Booleans

Write a function named higherPaid that takes two arguments, each an object representing an employee. The employee objects each have a salary property and the function should return the object representing the employee with the higher salary.

• Objects
• Booleans

Write a function isWinner that takes an object with a score property and returns true if the score is over 100 and false otherwise.

• Objects
• Arrays
• Control constructs

Write a function updateWins that takes an array of objects each with a score property and a wins property and updates each object by incrementing wins by one if the object is a winner according to the isWinner function you just wrote. After updating the objects, updateWins should return undefined.

• Objects
• Arrays
• Control constructs
• Booleans

Write a function bigWinners that takes an array of objects each with score and wins properties and returns an array containing the elements of the argument array whose wins property is over 10.

• Objects

Write a function named makeMove that takes three arguments: a string, specifying a mark (either 'X' or 'O'); a number specifying a row; and a number specifying a column. It should return an object with three properties, mark, row, and column, each with the value of the corresponding argument.

• Objects
• Arrays

Write a function named placeMark that takes a 3x3 array like the ones returned by makeBoard and an object like the ones returned by makeMove and sets the element of the array at the row and column specified in the move object to the move's mark.

The function does not need to return any specific value but after calling it the array passed as the first argument should be modified. For instance, after:

  let board = makeBoard();
  let move = makeMove('X', 1, 1);
  placeMark(board, move);

the expression board[1][1] should evaluate to 'X'.

• Objects
• Arrays

Write a function named recordMove that takes two arguments: an array and a move object, like the ones returned by makeMove. It should add the given move to the end of the array.

The function does not need to return any specific value but after it is called the array argument should be one longer than it was before the call and the last element of the array should be the object passed as the second argument.

• Objects
• Arrays

Write a function named rowForMove that takes two arguments: an array of move objects like the ones collected in recordMove and a number which is an index into that array. It should return the row value (a number) of the move at the given index.

For example after these two lines are executed:

   let moves = [];
   recordMove(moves, makeMove('X', 1, 2));

the call rowForMove(moves, 0) should return 1.

• Objects
• Arrays
• Control constructs

Write a function named placeMoves that takes two arguments: a 3x3 array like the ones returned by makeBoard and an array of moves such as might be built up by repeatedly calling recordMove. The function should call placeMark to place the mark for each move in the array of moves in the correct position on the board array.

The function does not need to return any specific value though obviously all the calls to placeMark will have updated the board array argument. For instance after these lines are executed:

   let moves = [];
   let board = makeBoard();
   recordMove(moves, makeMove('X', 1, 1));
   recordMove(moves, makeMove('O', 0, 0));
   recordMove(moves, makeMove('X', 0, 1));
   placeMoves(board, moves);
          

then the board should be in this state: [['O', 'X', ''], ['', 'X', ''], ['', '', '']]