javascript skontrolovať, či sa v poli
var extensions = ["image/jpeg","image/png","image/gif"];
if(extensions.indexOf("myfiletype") === -1){
alert("Image must be .png, .jpg or .gif");
}
js skontrolujte, či reťazec obsahuje z poľa
const found = arrayOfStrings.find(v => str.includes(v));