find substring in string javascript

var str = "Hello world, welcome to the universe.";

var n = str.includes("world");
 'Blue Whale'.includes('blue')  // returns false
var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);var str = "Hello world, welcome to the universe.";
var n = str.includes("world");const string = "foo";
const substring = "oo";

console.log(string.includes(substring));