Find the Even numbers in an Array using JavaScript

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Borislav Hadzhiev

Wed Oct 27 20212 min read

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Photo by Max Vertsanov

Find the Even Numbers in an Array #

To find the even numbers in an array:

  1. Call the filter() method, passing it a function.
  2. On each iteration, verify that the number doesn't have a remainder when divided by 2.
  3. The filter method returns a new array containing the elements that satisfy the condition.
index.js
const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9]; const even = arr.filter(number => { return number % 2 === 0; }); console.log(even); // ๐Ÿ‘‰๏ธ [2, 4, 6, 8]

The function we passed to the Array.filter method gets called with each element in the array.

If the function returns a truthy value, the element is included in the new array.

On each iteration, we use the modulo (%) operator to check if the number doesn't have a remainder when divided by 2.

If there is no remainder when the number is divided by 2, it's an even number.

Only even numbers satisfy our condition and will be included in the array that the filter method returns.

An alternative approach is to use the Array.forEach method.

To find the even numbers in an array:

  1. Create a new array that will store all even numbers.
  2. Use the forEach method to iterate over the array and verify if each number has a remainder when divided by 2.
  3. If there is no remainder, push the number to the even numbers array.
index.js
const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9]; const even = []; arr.forEach(number => { if (number % 2 === 0) { even.push(number); } }); console.log(even); // ๐Ÿ‘‰๏ธ [2, 4, 6, 8]

The function we passed to the forEach method gets called with each element in the array.

However, the forEach method doesn't return an array like filter does.

The forEach method returns undefined, so we have to create a new array to store the results.

Once the method has iterated over the entire array the even array will contain all even numbers from the original array.

Further Reading #

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