Get random value from array if it doesn't exist in another array

February 16, 2022

I have two arrays and I want to get a random new value from Array1, if the value isn’t included in Array2 already.

const array1 = ["Banana", "Orange", "Apple", "Mango"];
const array2 = ["Banana", "Mango"];

const randomElement = array1[Math.floor(Math.random() * array.length)];

I have already have a existing variable called randomElement, that finds a random element in Array 1 but it doesn’t look at whether the element already exists in Array 2 or not.

Ideally the variable randomElement should only currently output either "Orange" or "Apple" since they are the ones missing in Array 2. How do I go on about this task the easiest?

>Solution :

You need to compute the array having elements in array1 but not in array2 first, you can do this using Array#filter and Array#includes:

const array1 = ["Banana", "Orange", "Apple", "Mango"];
const array2 = ["Banana", "Mango"];

const array = array1.filter(e => !array2.includes(e));
const randomElement = array[Math.floor(Math.random() * array.length)];

console.log(randomElement);