//Checks whether element exists in array
const myArray = [2,3,4,5,6]
myArray.includes(2)
//true
myArray.includes(8)
//false
const newArra = [{id:1}, {id:2}, {id:3}]
//undefined
//first argument: searched number, second argument: index
//so: is at index 3 the number 2?
myArray.includes(2,3)
//false