Array manipulation is a common task in programming. Whether you are calculating a total for a shopping cart, grabbing only the first names from a list of people, or moving a piece on a chessboard, you are probably modifying or manipulating an array somewhere in the code.
- Fork this repo
- Clone it to your machine
- Clone the repository (it contains only the readme).
- Create a new branch from the master branch with your name in lowercase, without spaces, and without special characters.
- Create an index.html file in the project's root directory.
- Create a scripts.js file in the project's root directory.
- Develop the functions and tests described below in the script.js file and execute the functions in the index.html file (with console logs where it makes sense).
- Make a commit for each test executed.
- Upon completing the exercise, push to the repository.
Implement the function maxOfTwoNumbers that takes two numbers as arguments and returns the bigger number.
Implement the function findLongestWord that takes as an argument an array of words and returns the longest one. If there are 2 with the same length, it should return the first occurrence.
You can use the following array to test your solution:
const words = ['mystery', 'brother', 'aviator', 'crocodile', 'pearl', 'orchard', 'crackpot'];Calculating a sum can be as simple as iterating over an array and adding each of the elements together.
Implement the function named sumNumbers that takes an array of numbers as an argument and returns the sum of all the numbers in the array. Later in the course, we will learn how to do this using the reduce array method, making your work significantly easier. For now, let's practice the "declarative" way of adding values using loops.
You can use the following array to test your solution:
const numbers = [6, 12, 1, 18, 13, 16, 2, 1, 8, 10];In iteration 3, you created a function that returns the sum of an array of numbers. But what if we want to calculate the sum of the length of words in an array? What if it also includes boolean values? To achieve this, we must create a function allowing this flexibility.
You should implement the function sum() in this iteration. The function should take an array of mixed values - numbers, strings, and booleans. The function should add all the string lengths, numeric values, and numeric values of booleans to the total sum and return the sum.
You can use the following array to test your solution:
const mixedArr = [6, 12, 'miami', 1, true, 'barca', '200', 'lisboa', 8, 10];
// should return: 57Note: Your function should only accept an array with numbers, strings, or booleans. If the array contains any other data type, such as an object, you should throw an error. In JavaScript, the syntax for throwing an error is as follows:
throw new Error("Error message goes here");When specifying the error message, you should be specific and descriptive in explaining the error.
Calculating an average is a prevalent task. So let's practice it a bit.
The logic behind this:
- Find the sum as we did in the first exercise (or how about reusing the function
sumNumbers()?) - Divide that sum by the number of elements in the array.
Implement the function averageNumbers that expects an array of numbers and returns the average of the numbers.
You can use the following array to test your solution:
const numbers = [2, 6, 9, 10, 7, 4, 1, 9];Implement the function named averageWordLength that receives as a single argument an array of words and returns the average length of the words:
You can use the following array to test your solution:
const words = ['seat', 'correspond', 'linen', 'motif', 'hole', 'smell', 'smart', 'chaos', 'fuel', 'palace'];Create function avg(arr) that receives any mixed array and calculates the average. For example, consider an array filled with numbers and/or strings and/or booleans as a mixed array.
The non-numerical values should be counted as follows:
- Booleans:
truecounts as1andfalsecounts as0. - Strings: use the string
lengthas the numeric value.
const mixedArr = [6, 12, 'miami', 1, true, 'barca', '200', 'lisboa', 8, 10];
// should return: 5.7Take the following array, remove the duplicates, and return a new array. You are more than likely going to want to check out the Array methods indexOf and includes.
Do this in the form of a function uniquifyArray that receives an array of words as an argument.
You can use the following array to test your solution:
const words = [
'crab',
'poison',
'contagious',
'simple',
'bring',
'sharp',
'playground',
'poison',
'communion',
'simple',
'bring'
];Let's create a simple array search.
Declare a function named doesWordExist that will take in an array of words as one argument and a word to search for as the other. Return true if the word exists in the array; otherwise, return false.
You can use the following array to test your solution:
const words = ['machine', 'subset', 'trouble', 'starting', 'matter', 'eating', 'truth', 'disobedience'];Declare a function named howManyTimes that will take in an array of words as the first argument and a word to search for as the second argument. The function will return the number of times that word appears in the array.
You can use the following array to test your solution:
const words = [
'machine',
'matter',
'subset',
'trouble',
'starting',
'matter',
'eating',
'matter',
'truth',
'disobedience',
'matter'
];Given multiple arrays, find the greatest product of four adjacent numbers.
We consider adjacent any four numbers that are next to each other horizontally or vertically. For example, if we have a 5x5 Matrix like:
[ 1, 2, 3, 4, 5]
[ 1, 20, 3, 4, 5]
[ 1, 20, 3, 4, 5]
[ 1, 20, 3, 4, 5]
[ 1, 4, 3, 4, 5]The greatest product will be the 20x20x20x4 = 32000.
Declare a function named greatestProduct(matrix) to find it in the 20×20 grid below!
const matrix = [
[08, 02, 22, 97, 38, 15, 00, 40, 00, 75, 04, 05, 07, 78, 52, 12, 50, 77, 91, 08],
[49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 04, 56, 62, 00],
[81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 03, 49, 13, 36, 65],
[52, 70, 95, 23, 04, 60, 11, 42, 69, 24, 68, 56, 01, 32, 56, 71, 37, 02, 36, 91],
[22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80],
[24, 47, 32, 60, 99, 03, 45, 02, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50],
[32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70],
[67, 26, 20, 68, 02, 62, 12, 20, 95, 63, 94, 39, 63, 08, 40, 91, 66, 49, 94, 21],
[24, 55, 58, 05, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72],
[21, 36, 23, 09, 75, 00, 76, 44, 20, 45, 35, 14, 00, 61, 33, 97, 34, 31, 33, 95],
[78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 03, 80, 04, 62, 16, 14, 09, 53, 56, 92],
[16, 39, 05, 42, 96, 35, 31, 47, 55, 58, 88, 24, 00, 17, 54, 24, 36, 29, 85, 57],
[86, 56, 00, 48, 35, 71, 89, 07, 05, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58],
[19, 80, 81, 68, 05, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 04, 89, 55, 40],
[04, 52, 08, 83, 97, 35, 99, 16, 07, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66],
[88, 36, 68, 87, 57, 62, 20, 72, 03, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69],
[04, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 08, 46, 29, 32, 40, 62, 76, 36],
[20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 04, 36, 16],
[20, 73, 35, 29, 78, 31, 90, 01, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 05, 54],
[01, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 01, 89, 19, 67, 48]
];Following the logic you've used in iteration #8.1, declare a function called greatestProductOfDiagonals(matrix). It takes a matrix as a parameter and returns the greatest product of any four values laid out diagonally, in either direction.
Happy coding! ❤️
I am stuck in the exercise and don't know how to solve the problem or where to start.
If you are stuck in your code and don't know how to solve the problem or where to start, you should take a step back and try to form a clear question about the specific issue you are facing. This will help you narrow down the problem and come up with potential solutions.
For example, is it a concept that you don't understand, or are you receiving an error message that you don't know how to fix? It is usually helpful to try to state the problem as clearly as possible, including any error messages you are receiving. This can help you communicate the issue to others and potentially get help from classmates or online resources.
Once you have a clear understanding of the problem, you will be able to start working toward the solution.
All of the Jasmine tests are failing and in red. Why did this happen?
One possible reason why all of the Jasmine tests are failing is that there is a syntax error in the code being tested. If the code contains a syntax error, it will not be loaded properly and none of the tests will be able to run. This will cause all of the tests to fail.
To troubleshoot this issue, you will need to examine the code being tested for syntax errors. Look for missing brackets, semicolons, or other syntax issues that could be causing the problem. If you find a syntax error, correct it and try running the tests again.
Another possibility is that there is an issue with the tests. It is possible that you may have modified the test file and caused an issue. If you have made changes to the test file, try copying and pasting the original test file and running the tests again to see if this resolves the issue.
How do you find a length of a string in JavaScript?
To find the length of a string, use the length property. Here is an example:
const str = "Hello, world!"";
console.log(str.length); // 13The length property returns the number of characters in the string, including spaces and special characters.
How do I loop over an array?
Loops allow you to repeat a block of code a certain number of times. There are several ways to loop over an array in JavaScript:
The for loop is the most traditional way to loop through an array in JavaScript. It consists of three parts: the initialization, the condition, and the increment/decrement:
const animals = ['cat', 'dog', 'bird'];
// initialize counter variable (let i = 0)
// set condition (i < animals.length)
// increment counter (i++)
for (let i = 0; i < animals.length; i++) {
console.log(animals[i]);
}In initialization, you declare a counter variable and set its initial value.
The condition is a boolean expression that is evaluated before each iteration of the loop. If the condition is true, the loop will continue. Once the condition turns false, the loop will terminate.
The increment/decrement is where you update the counter variable and it happens at the end of each iteration.
The block of code inside the loop is repeated during each iteration.
The while loop is another way to loop through an array in JavaScript. It consists of a condition and a block of code that is executed as long as the condition is true.
Like the for loop, the while loop requires a counter variable to keep track of the current position in the array. The counter variable must be initialized before the loop and incremented or decremented at the end of each iteration.
const animals = ['cat', 'dog', 'bird'];
// initialize a counter variable (i)
let i = 0;
// set condition (i < animals.length)
while (i < animals.length) {
console.log(animals[i]);
// increment counter (i++)
i++;
}How do I loop over an array using the forEach() method?
The forEach() method executes a provided function once for each array element. It does not return a new array but rather executes the function on each element in the array.
The syntax of the forEach() method is as follows:
array.forEach( function(element) {
// code to be executed for each element
});Here is an example that uses the forEach() method to log each element and its index in an array to the console:
const fruits = ['apple', 'banana', 'cherry'];
fruits.forEach( function(element, index) {
console.log(`${index}: ${element}`);
});You can also use an arrow function as the callback function for forEach():
fruits.forEach((element, index) => {
console.log(`${index}: ${element}`);
});What could cause array.length to return undefined?
If you try to access the .length property on an array (e.g., array.length) but get undefined, it means that the variable you are accessing is not actually an array.
How do I fix this?
Check that the variable you are trying to access is actually an array.
Why is my function returning the last element of the array instead of the longest one?
Your function might not be correctly checking for the longest element in the array. In other words, there may be an issue with the logic of the conditional statements in the function or with the comparison being used in the conditionals.
To fix this issue, you should check the logic of the conditional statements in the function.
How can I compare the length of each word in an array in JavaScript?
To compare the length of each word in an array in JavaScript, you can use a loop to iterate through the array and compare the length of each element using the .length property.
Here is an example of how you loop over an array:
function findLongestWord(words) {
for (let i = 0; i < words.length; i++) {
console.log(words[i]);
}
}To compare the length of each element, you should use a conditional statement in the following way:
if ( words[i].length > longestWord.length) {
console.log(`${words[i].length} is longer than ${longestWord.length}`);
}