в массиве в JS
var letters = ["A", "B", "C", "D"];
var result = letters.includes("A");
// result will be TRUE or FALSE
Terrible Tern
var letters = ["A", "B", "C", "D"];
var result = letters.includes("A");
// result will be TRUE or FALSEvar fruits = ["Banana", "Orange", "Apple", "Mango"];
var n = fruits.includes("Mango");const found = arr1.some(r=> arr2.indexOf(r) >= 0)