How can I check if a JavaScript array includes a specific value?

Angelos Chalaris · JavaScript, Array · Sep 18, 2022

Primitive values

You can use Array.prototype.includes() to check if an array contains a primitive value. This is the most convenient option when working with strings, numbers, booleans, symbols, null or undefined. You can even specify an index as a secondary parameter to start searching from.

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

array.includes(3); // true
array.includes(6); // false
array.includes(3, 3); // false

Objects

Unlike primitive values, you can't use Array.prototype.includes() to check if an array includes an object. This comes down to how JavaScript compares values and the fact that objects are reference types. I highly recommend reading the previous article about object comparison, as I won't be going into detail on how to compare objects here.

Due to this difference between primitive values and objects, you can't use Array.prototype.includes() to check if an array includes an object. However, provided you implement a deep equality function, you can use Array.prototype.some() to check if any object matches the shape of another object.

const array = [{ a: 1 }, { a: 2 }, { a: 3 }];

const equals = (a, b) => Object.keys(a).every(key => a[key] === b[key]);

array.some(item => equals(item, { a: 2 })); // true
array.some(item => equals(item, { a: 4 })); // false

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