javascript check if value in array

var fruits = ["Banana", "Orange", "Apple", "Mango"];

var n = fruits.includes("Mango");
 

var colors = ["red", "blue", "green"];
var hasRed = colors.includes("red"); //true
var hasYellow = colors.includes("yellow"); //false

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var n = fruits.includes("Mango");
 

var fruits = ["Banana", "Orange", "Apple", "Mango"];

var n = fruits.includes("Mango");

var myList=["a", "b", "c"];
mylist.includes("d")//returns true or false

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var n = fruits.includes("Mango");

function isArray(value) {
    return Object.prototype.toString.call(value) === "[object Array]";
}

var extensions = ["image/jpeg","image/png","image/gif"];          
if(extensions.indexOf("myfiletype") === -1){
	alert("Image must be .png, .jpg or .gif");
}