Check if an array contains an element in JavaScript

In JavaScript, there are a few ways to check if an array contains an element. Depending on if you need to know if it contains an exact value, or match a criteria, you have different options.

Using Array.includes to check for an exact value

With Array.includes() you can check that your array contains an exact value you are looking for. For example:

const trees = ['oak', 'willow', 'maple', 'yew', 'magic'];

console.log(trees.includes('oak')); // true
console.log(trees.includes('normal')); // false

However, if your array contains objects, Array.includes() may not work as expected because it checks for the same object reference, not just the content. Also, it won’t be sufficient if you need to perform more specific checks.

const trees = [
    {name: 'oak'},
    {name: 'willow'},
    {name: 'maple'},
    {name: 'yew'},
    {name: 'magic'},
];

console.log(trees.includes({name: 'oak'})); // false

Using Array.find() and Array.some()

In the case of objects, or having to do specific checks, you can use the find and some functions. They both work the same, except that find will return the value it found or undefined if nothing was found, while some will return true if any values match, and false if they don’t. Both functions will stop the moment they find any value that matches. So if you have multiple values that match your check, the first one will be returned.

To give some examples:

const trees = [
    {name: 'oak'},
    {name: 'willow'},
    {name: 'maple'},
    {name: 'yew'},
    {name: 'magic'},
];

console.log(trees.find((tree) => tree.name === 'oak')); // {name: 'oak'}
console.log(trees.some((tree) => tree.name === 'oak')); // true

console.log(trees.find((tree) => tree.name === 'normal')); // undefined
console.log(trees.some((tree) => tree.name === 'normal')); // false

console.log(trees.find((tree) => tree.name.length > 3)); // {name: 'willow'}

With these array method you can easily check if your javascript array contains a specific item, wheter you are dealing with simple values or complex objects.

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