Check if an element is present in an array using JavaScript

Checking if an element is present in an array using JavaScript involves iterating through the array and comparing each element with the target value. If a match is found, the element is considered present; otherwise, it's absent.

There are different approaches to finding an element present in an array, which is described below:

Using includes() method

This method can be utilized to find whether a particular element is present in the array or not. it returns true or false i.e., If the element is present, then it returns true otherwise false. 

Example: In this example, the array is declared and by using the includes() method, & we can check the value present in the array.

// Define an array
const arr = [21, 12, 13, 45, 54];

// Check if the array includes the value 12
if (arr.includes(12)) {
    console.log("12 is present in the array.");
} else {
    console.log("12 is not present in the array.");
}

Output:

12 is present in the array

Using the indexOf() method

This method can be used to find the index of the first occurrence of the search element provided as the argument to the method. 

Example: In this example, an array is declared and by using indextOf() function, we can check the value present in the array.

// Define an array
const arr = [10, 72, 3, 14, 5];

// Check if the array includes the value 3
if (arr.indexOf(3) >= 0) {
    console.log("3 is present in the array.");
} else {
    console.log("3 is not present in the array.");
}

Output:

3 is present in the array

Using the find() method

This method is used to get the value of the first element in the array that satisfies the provided condition. It checks all the elements of the array and whichever the first element satisfies the condition is going to print.

Example: In this example, an array is declared, and by using the find() function, we can check the value present in the array.

// Define an array
const arr = [5, 20, 30, 40, 50];

// Use the find() method to check if the
// value 30 is present in the array
const result = arr.find(element => element === 30);

// Check the result and log a message
if (result !== undefined) {
    console.log("30 is present in the array.");
} else {
    console.log("30 is not present in the array.");
}

Output:

30 is present in the array

Using the for() Loop

The for loop facilitates the execution of a set of instructions repeatedly until some condition evaluates and becomes false.

Example: In this example, an array is declared by using for() loop iteration up to the element found. By using this, we can check whether the value present in the array or not.

// Define an array
const array1 = [13, 23, 33, 43, 53];

// Initialize a flag variable
let p = false;

// Iterate through the array and check each element
for (let i = 0; i < array1.length; i++) {
    if (array1[i] === 53) {
        p = true;
        break;
    }
}

// Check the flag variable and log a message
if (p) {
    console.log("53 is present in the array.");
} else {
    console.log("53 is not present in the array.");
}

Output:

53 is present in the array

Using the Array.some() method

Algorithm: 

• Initialize the array. 
• Use some method on for loop with some condition which matches the required element and returns true if matches. 
• Print the evaluated result.  

Example:  By using some(), we can check the value present in the array or not.

// Define an array
const arr = [5, 20, 30, 40, 50];

// Use the some() method to check if the
// value 30 is present in the array
const result = arr.some(element => element === 30);

// Check the result and log a message
if (result !== undefined) {
    console.log("30 is present in the array.");
} else {
    console.log("30 is not present in the array.");
}

Output:

30 is present in the array.

Time complexity: O(N), Where N is the length of the Array. 

Auxiliary complexity: O(1), Because no extra space is used. 

Using a filter() method

Using the filter() method in JavaScript, you can check if an element is present in an array by filtering the array for the element and then checking if the resulting array's length is greater than zero. This approach is efficient and concise.

Example:

const arr = [1, 2, 3, 4, 5];

const checkElement = (array, element) => array.filter(el => el === element).length > 0;

const isThreePresent = checkElement(arr, 3);
const isEightPresent = checkElement(arr, 8);

console.log(isThreePresent); // true
console.log(isEightPresent); // false

true
false

Using Set for Efficient Element Checking

The Set object in JavaScript stores unique values of any type, including primitive types and object references. By converting the array into a Set, we can take advantage of its quick lookup capabilities using the has() method.

Example: Using a Set for checking element presence in an array provides an elegant and efficient solution, enhancing code readability and performance compared to traditional iteration-based methods. It's a modern approach that leverages JavaScript's built-in data structures for optimal results.

// Define an array
const arr = [1, 2, 3, 4, 5];

// Convert the array into a Set
const set = new Set(arr);

// Function to check if an element exists in the array
const isElementPresent = (array, element) => set.has(element);

// Usage examples
console.log(isElementPresent(arr, 3)); // true
console.log(isElementPresent(arr, 8)); // false

true
false