Mohib Khan
Mohib's blog

Follow

Mohib's blog

Follow
List Of Array Methods To Manipulate Your Arrays

List Of Array Methods To Manipulate Your Arrays

Mohib Khan's photo
Mohib Khan
ยทAug 26, 2021ยท

4 min read

Does it happen with you that you learned about all the array methods at the beginning of your Web Dev learning journey? Then you only remember a handful of them. The ones that are often used like map(), filter(), forEach().

And you end up doing something like:

function checkAllDateFormatsForPalindrome(date) {
  const dateArray = getAllDateFormats(date);

  const palindromes = dateArray.filter((date) => isPalindrome(date));
  return palindromes.length;
}


// usage of the function checkAllDateFormatsForPalindrome
if (checkAllDateFormatsForPallindrome(date)) {
      output.innerHTML = `Yay! Your birthday is a palindrome ๐Ÿš€`;
    } 

// rest of the code

Here, I was checking if the dateArray contains a date that qualifies as a Palindrome using a filter function. Then returning the length of the const palindromes which will return length. However, I don't need the length, I only needed a bool value.

So, instead of using filter() we can directly use some() method. And it will return a bool value. The some() method checks if at least one element passes the test condition in the provided calling function.

So, the checkAllDateFormatsForPalindrome() function looks like this now:

//refactored checkAllDateFormatsForPalindrome() function
function checkAllDateFormatsForPalindrome(date) {
  const dateArray = getAllDateFormats(date);

  return dateArray.some((date) => isPalindrome(date));
}

So, writing this blog so that I come back again and again to find an array method that will be helpful for a situation like the above.

  • map

    The map method creates a new array by iterating through the elements and calling a provided function on every element.
const arrayOfNumbers = [2, 4, 6, 8, 10];

const mappedArray = arrayOfNumbers.map(num=> num/ 2);

console.log(mappedArray) // [1, 2, 3, 4, 5]
  • filter

    The filter method creates a new array with the elements that pass a given condition in the calling function.
const arrayOfNumbers = [3, 4, 5, 8, 12, 15];

const filteredArray = arrayOfNumbers.filter((num) => num% 2 === 0);

console.log(filteredArray); // [4, 8, 12]
  • reduce

    The reduce method calls a defined reducer function for each element and returns a single value.
const arrayOfNumbers = [3, 4, 5, 8, 2, 15];

const reducedValue = arrayOfNumbers.reduce((total, current) => total + current);

console.log(reducedValue); // 37
  • find

    The find method returns the first element that passes the given condition in the calling function
const arrayOfNumbers = [3, 4, 5, 8, 2, 15];

const numberFound = arrayOfNumbers.find((num) => num > 4);

console.log(numberFound); // 5
  • findIndex

    The findIndex method is very similar to the find method, except it returns the index of the first element that passes the given condition in the calling function
const arrayOfNames = [
  "Chanakya",
  "Maharana Pratap",
  "Shershaah",
  "Charak",
  "Sangram",
];

const indexOfName = arrayOfNames.findIndex((item) => item === "Shershaah");

console.log(indexOfName); // 2
  • forEach

    The forEach method iterates through all the elements of an array and calls a provided function for each element.
const arrayOfNames = [
  "Chanakya",
  "Maharana Pratap",
  "Shershaah",
  "Charak",
  "Sangram",
];

arrayOfNames.forEach((item) => console.log(item));
// Chanakya
// Maharana Pratap
// Shershaah
// Charak
// Sangram

The difference between map() & forEach() is that, the former returns a new array and the latter returns undefined.

  • every

    The every() method checks if all elements pass the test condition in the provided calling function. It also returns a boolean value.
const arrayOfNames = [
  "Chanakya",
  "Maharana Pratap",
  "Shershaah",
  "Charak",
  "Sangram",
];

const doesContainName = arrayOfNames.every((item) => item === "Shershaah");

console.log(doesContainName); // false
  • some

    The some() method checks if at least one element passes the test condition in the provided calling function. It returns a boolean value. The difference between some() & every() methods is that some() method stops checking as soon as the test condition is true. On the other hand, every() keeps checking until the last item in the array.
const arrayOfNames = [
  "Chanakya",
  "Maharana Pratap",
  "Shershaah",
  "Charak",
  "Sangram",
];

const doesContainName = arrayOfNames.some((item) => item === "Shershaah");

console.log(doesContainName); // true
  • includes()

    The includes() method checks if the array contains a particular value that is passed as an argument. It returns a bool value.
const arrayOfNames = [
  "Chanakya",
  "Maharana Pratap",
  "Shershaah",
  "Charak",
  "Sangram",
];

const doesContainName = arrayOfNames.includes("Shershaah");

console.log(doesContainName); // true
ย 
Share this