findInArray.js

const items = [1, 2, 3, 4, 5 ]; 

if(items.includes(5)){ 
  console.log(true) // true
} 

if(items.indexOf(5) > -1){
  console.log(true); // true ;
}

console.log(items.indexOf(6) >= -1) // true
console.log(items.includes(6)) // false