JavaScript program to print even numbers in an array

Given an array of numbers and the task is to write a JavaScript program to print all even numbers in that array.

We will use the following methods to find even numbers in an array:

Example:

Input:    numbers_array1= [4, 76, 89, 61, 72, 64]
Output: [4,76,72,64]
Input:   numbers_array2= [15, 60, 90, 14, 7, 45]
Output: [60,90,14]

Method 1: Using for Loop 

• Iterate each element in the array using for loop to check if (num %2==0), the condition to check even or not. 
• If the condition is satisfied then push the num into the even list. 
• After iterating all elements in an array print the even list.

Example: In this example, we are Using for Loop

// Initializing numbers array
let numbers = [10, 23, 12, 21];

// Declaring empty Even array
let even = [];
for(let i = 0; i < numbers.length; i++) {
       if (numbers[i] % 2 == 0)
       even.push(numbers[i]);
}

// Printing output
console.log(`Even numbers in an array are: ${even}`);

Even numbers in an array are: 10,12

Method 2: Using while Loop 

• Iterate through the array using the while loop.
• Check elements if (element%2==0) condition satisfies, we push the element into an even array. 
• After iterating all elements using a while loop, we print an even numbers array.

Example: In this example, we are Using while Loop 

// Initializing numbers array
let numbers=[44, 26, 48, 64, 27, 53];

// Declaring empty Even array
let even = [];
let i = 0;
while(i < numbers.length) {
       if (numbers[i] % 2 == 0)
       even.push(numbers[i]);
       i++;
}

// Printing output
console.log(`Even numbers in an array are: ${even}`)

Even numbers in an array are: 44,26,48,64

Method 3: Using forEach Loop

• Declare an array called "numbers" containing a set of integers.
• Declare an empty array called "even".
• Use the forEach method to iterate through each element in the "numbers" array.
• Within the forEach loop, use an if statement to check if the current element is even using the modulus operator (element%2==0).
• If the element is even, use the push method to add it to the "even" array.
• After the forEach loop, use console.log () to display the message "Even numbers in an array are: [even numbers]" where [even numbers] is the array of even numbers.

This approach allows one to iterate through the entire array, check each element for even-ness, and add even numbers to a separate array, which is then displayed in the console.

Example: In this example, we are Using forEach Loop

// Initializing numbers array
let numbers = [86, 41, 55, 85, 90, 24];

// Declaring empty Even array
let even = [];
numbers.forEach(element => {
    if( element%2 == 0 )
    even.push(element);
});

// Printing output
console.log(`Even numbers in an array are: ${even}`);

Even numbers in an array are: 86,90,24

Method 4: Using filter Method

• Declare an array called "numbers" containing a set of integers.
• Use the filter() method on the "numbers" array, passing in a callback function as the argument.
• The callback function should take in the current element as a parameter and use the modulus operator (element%2==0) to check if it is even.
• Return true for even numbers and false for odd numbers in the callback function.
• Assign the returned result of the filter method to a variable, let's say 'evenNumbers'.
• After the filter method, use console.log() to display the message "Even numbers in an array are: [evenNumbers]" where [evenNumbers] is the array of even numbers returned from the filter method.

The filter method returns a new array with all elements that pass the test implemented by the callback function.

Example: In this example, we are Using filter Method

// Initializing numbers array
let numbers = [86, 41, 55, 85, 90, 24];

let evenNumbers = numbers.filter(function(element) {
      return element % 2 === 0;
});

// Printing output
console.log(`Even numbers in an array are: ${evenNumbers}`);

Even numbers in an array are: 86,90,24

Method 5: Using for...of Loop

The for…of loop iterates over the iterable objects (like Array, Map, Set, arguments object, …,etc), invoking a custom iteration hook with statements to be executed for the value of each distinct property.

Example: In this example, we are Using for...of Loop

const even = [];
const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
for (const num of arr) {
    if (num % 2 === 0) {
        even.push(num);
    }
}
console.log(even);

[ 2, 4, 6, 8 ]

Method 6: Using reduce

In this approach we use reduce method to iterate over the array and print the event the even numbers.

Example: In this example, we are Using reduce method

let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
const ans = [];

numbers.reduce(function(acc, number) {
    if (number % 2 === 0) {
        ans.push(number)
    }
    return acc;
}, []);
console.log(ans)

[ 2, 4, 6, 8, 10 ]