Modern browsers have Array#includes, which does exactly that and is widely supported by everyone except IE:

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console.log(['joe', 'jane', 'mary'].includes('jane')); //true

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

fruits.includes("Mango");

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

​

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

​

var n = fruits.includes("Django"); // false

wordsArray = ['hello', 'to', 'nice', 'day']

yourString = 'Hello. Today is a nice day'.toLowerCase()

result = wordsArray.every(w => yourString.includes(w))

console.log('result:', result)

const found = arrayOfStrings.find(v => str.includes(v));

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

​

let result = ratings.includes(4); 

console.log(result); // true

​

result = ratings.includes(6); 

console.log(result); // false

var arr = ["name", "id"];

  if (arr.indexOf("name") > -1) console.log('yeah');

  else console.log('nah');

var extensions = ["image/jpeg","image/png","image/gif"];          

if(extensions.indexOf("myfiletype") === -1){

    alert("Image must be .png, .jpg or .gif");

} 

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

​

let result = ratings.includes(4); 

console.log(result); // true

​

result = ratings.includes(6); 

console.log(result); // false

const nums = [ 1, 3, 5, 7];

console.log(nums.includes(3));

// true