Find a Substring inside a String in JavaScript

How to use JavaScript to find a substring inside a string.

Let’s assume we have a secret passcode yacine and want to check if it exists in another string.

Here we’ll use findme to demonstrate the string we want to check:

const passcode = "yacine";
const findme = `8sowl0xeyacinexjwo98w`;

Visually we can see that findme contains yacine but how do we get a yes/no answer in JavaScript?

We can introduce a new feature in ES6, the String.prototype.includes method, which will return us a Boolean value based on whether the substring was found:

const found = findme.includes(passcode);
// true
console.log(found);

const index = findme.indexOf(passcode);

// true
const passcode = "yacine";
const findme = `8sowl0xe${passcode}xjwo98w`;

// ES6 String.prototype.includes
console.log(findme.includes(passcode));

// String.prototype.indexOf
console.log(findme.indexOf(passcode) !== -1);

const index = findme.indexOf(passcode);

// true
console.log(!!~index);

Thanks for reading!