Below shows a typical use of the array method includes.
Additionally a template literal is used below with a placeholder ${userJohnExists} adding to the terseness of the code. Note that back-ticks (`) are used to denote a template literal.
const users = ["john", "derek", "tracey", "anna"];
let userJohnExists = users.includes("john");
console.log(`John exists: ${userJohnExists}`);
Output will be:
John exists: true