JavaScript - Find an Item in an Array

Here are the various methods to find an item in an array in JavaScript

1. Using the includes() method

The includes() method checks if an array includes a certain value, returning the boolean value true or false accordingly.

const a = ['apple', 'banana', 'orange'];
console.log(a.includes('banana'));
console.log(a.includes('grapes')); 

true
false

In this example

• a.includes('banana') checks if the array contains the string 'banana', and returns true because 'banana' is present.
• a.includes('grapes') checks if the array contains the string 'grapes', and returns false because 'grapes' is not in the array.

2. Using the indexOf() method

The indexOf() method returns the index of the first occurrence of a specified value in an array, or -1 if it is not found.

const a  = ['apple', 'banana', 'orange'];
console.log(a.indexOf('banana')); 
console.log(a.indexOf('grapes')); 

1
-1

In this example

• a.indexOf('banana') returns 1, the index of 'banana' in the array.
• a.indexOf('grapes') returns -1 because 'grapes' is not found in the array.

3. Using the find() method

The find() method returns the value of the first element in an array that satisfies a provided testing function, or undefined if no values satisfy the function.

const a = ['apple', 'banana', 'orange'];
const res = a.find(fruit => fruit === 'banana');
if (res) {
    console.log("banana is present in the array");
} else {
    console.log("banana is not present in the array");
};

banana is present in the array

In this example

• The find() method searches for 'banana' in the array and returns the first match, which is 'banana'.
• Since 'banana' is found, the message "banana is present in the array" is logged to the console.

4. Using Array.some() method

The some() method tests whether at least one element in the array passes the provided function

const a = [1, 2, 3, 4, 5];
const res = a.some(num => num > 3);
console.log(res); 

true

In this example

• The some() method checks if any element in the array is greater than 3.
• Since 4 and 5 satisfy the condition, the output is true.

5. Using forEach Loop

Using a forEach loop, iterate through each element in the array. Within the loop, check if the current element matches the target item.

let a = [1, 2, 3, 4, 5];
let found = false;

a.forEach(element => {
    if (element === 3) {
        found = true;
    }
});

console.log(found);

true

In this example

• The forEach() method iterates through the array to check if any element is equal to 3.
• Once it finds 3, it sets found to true, and the result is logged as true.

6. Using the filter() method

The filter() method creates a new array with all elements that pass the test implemented by the provided function.

const a = [1, 2, 3, 4, 5];
const res = a.filter(a => a === 3);

if (res.length > 0) {
    console.log("3 is found in the array.");
} else {
    console.log("3 is not found in the array.");
}

3 is found in the array.

In this example

• The filter() method creates a new array containing elements that are equal to 3.
• If the length of the result array is greater than 0, it logs "3 is found in the array.", otherwise "3 is not found in the array."

7. Using the Set and has() Method

The Set object in JavaScript stores unique values. The has() method checks if a specific value exists in the Set.

const a = new Set(['apple', 'banana', 'orange']);
console.log(a.has('banana')); 
console.log(a.has('grapes')); 

true
false

In this example

• a.has('banana') returns true because 'banana' exists in the Set.
• a.has('grapes') returns false because 'grapes' is not in the Set.

8. Using Array.prototype.reduce()

The reduce() method executes a reducer function (that you provide) on each element of the array, resulting in a single output value.

const a = [1, 2, 3, 4, 5];
const tar = 3;
const item = a.reduce((found, item) => {
    if (found) {
        return true;
    }
    return item === tar;
}, false);

if (item) {
    console.log(`${tar} is found in the array.`);
} else {
    console.log(`${tar} is not found in the array.`);
}

3 is found in the array.

In this example

• The reduce() method is used to iterate over the array and check if any element equals tar (3).
• If the element matches tar, it returns true; otherwise, it returns false and continues the iteration.
• The result is logged based on whether tar is found in the array.