A robust & optimized String.prototype.contains polyfill, based on the ECMAScript 6 specification.

ES6 String.prototype.contains polyfill

A robust & optimized ES3-compatible polyfill for the String.prototype.contains method in ECMAScript 6.

Other polyfills for String.prototype.contains are available:

In a browser:

<script src="contains.js"></script>

Via npm:

npm install string.prototype.contains

Then, in Node.js:

// On Windows and on Mac systems with default settings, case doesn’t matter, 
// which allows you to do this instead: 

Polyfills + test suites for String.prototype.startsWith and String.prototype.endsWith are available, too.

Mathias Bynens

This polyfill is available under the MIT license.