How to Check if Multiple Values Exist in a JavaScript Array

To check if multiple values exist in a JavaScript array, you can use several methods depending on your needs. Here are some common approaches:

1. Using `Array.prototype.every()`#

The every() method tests whether all elements in the array pass the test implemented by the provided function. This is useful if you want to check if all of the specified values exist in the array.

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

const allExist = valuesToCheck.every((value) => array.includes(value));

console.log(allExist); // true if all values exist, false otherwise

2. Using `Array.prototype.some()`#

The some() method tests whether at least one element in the array passes the test implemented by the provided function. This is useful if you want to check if any of the specified values exist in the array.

const array = [1, 2, 3, 4, 5];
const valuesToCheck = [2, 6];

const anyExist = valuesToCheck.some((value) => array.includes(value));

console.log(anyExist); // true if any value exists, false otherwise

3. Using a Set for Faster Lookups#

If you have a large array or need to perform this check multiple times, converting the array to a Set for faster lookups can be more efficient.

const array = [1, 2, 3, 4, 5];
const valuesToCheck = [2, 4, 5];
const arraySet = new Set(array);

const allExist = valuesToCheck.every((value) => arraySet.has(value));

console.log(allExist); // true if all values exist, false otherwise

4. Using `filter()` and `length`#

You can use filter() to find which of the values exist in the array and then check if the count matches the number of values you wanted to check.

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

const foundValues = valuesToCheck.filter((value) => array.includes(value));

const allExist = foundValues.length === valuesToCheck.length;

console.log(allExist); // true if all values exist, false otherwise

5. Custom Function for Multiple Checks#

If you need to perform complex checks or need more control, you can write a custom function to check multiple values.

function checkValuesExist(array, values) {
    const set = new Set(array);
    return values.every((value) => set.has(value));
}

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

const allExist = checkValuesExist(array, valuesToCheck);

console.log(allExist); // true if all values exist, false otherwise

Summary#

every(): Use this method to check if all values exist.
some(): Use this method to check if any value exists.
Set: Convert the array to a Set for faster lookups, especially useful with large arrays.
filter(): Use this method to find which values exist and compare lengths.
Custom Function: Create a custom function for more complex checks or repeated use.

Choose the method that best fits your use case based on performance needs and the specifics of the check you are performing.