Add JS array includes

blog_posts/javascript-array-includes-value.md

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+---
+title: How can I check if a JavaScript array includes a specific value?
+shortTitle: JavaScript array includes value
+type: question
+tags: javascript,array
+expertise: beginner
+author: chalarangelo
+cover: blog_images/bridge-drop.jpg
+excerpt: Checking if an array includes a specific value is pretty straightforward, except when it comes to objects.
+firstSeen: 2022-09-18T05:00:00-04:00
+---
+
+### 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.
+
+```js
+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](/articles/s/javascript-pass-by-reference-or-pass-by-value). I highly recommend reading the previous article about [object comparison](/articles/s/javascript-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](/js/s/equals), you can use `Array.prototype.some()` to check if any object matches the shape of another object.
+
+```js
+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
+```