How to Check if a Value Exists in an Array in JavaScript

Check if a Value Exists in an Array in JavaScript

In this tutorial, we'll explore the most popular and beginner-friendly methods to check if an item exists in an array.

Method 1: Using includes()

The includes() method is the cleanest and most intuitive way to check for the presence of a value. It returns true if the item exists, and false otherwise. It's case-sensitive and works on both primitive values and strings.

const fruits = ["apple", "banana", "cherry"];

const hasBanana = fruits.includes("banana");
console.log("Does the array include 'banana'?", hasBanana);

Does the array include 'banana'? true

Method 2: Using indexOf() – The Legacy Approach

Before includes() came along, developers used indexOf() to check for existence. It returns the index of the first match or -1 if not found. While a bit more verbose, it still gets the job done.

indexOf. Check if the result is not -1 to determine presence.",
  "Print the result to console."
]' data-output-container="output_2" data-output-lines="0,0,1">const items = ["Item 1", "Item 2", "Item 3"];

const exists = items.indexOf("Item 2") !== -1;
console.log("Is 'Item 2' in the list?", exists);

Is 'Item 2' in the list? true

Method 3: Using some() – Flexible and Powerful

The some() method is ideal when your check involves a condition, not just a fixed value. For example, you might want to know if there’s a fruit that starts with the letter “c”. This method returns true as soon as one item satisfies the condition.

const fruits = ["apple", "banana", "cherry", "date"];

const hasC = fruits.some(fruit => fruit.startsWith("c"));
console.log("Is there a fruit that starts with 'c'?", hasC);

Is there a fruit that starts with 'c'? true

When Should You Use Each Method?

Use includes() when you're checking for the existence of a simple string, number, or boolean in an array. It’s the cleanest and most readable option. Go for indexOf() if you’re working in older environments or want to retrieve the item's position. Choose some() when the condition is more dynamic—like checking string patterns, object properties, or custom logic.