# is-defined [![Build Status](https://travis-ci.org/bendrucker/is-defined.svg?branch=master)](https://travis-ci.org/bendrucker/is-defined) > Check if an identifier is defined ## Install ``` $ npm install --save is-defined ``` ## Usage ```js var isDefined = require('is-defined') isDefined('window') //=> typeof window !== 'undefined' ``` ## API #### `isDefined(identifier)` -> `string` ##### identifier *Required* Type: `string` A JavaScript identifier. ## License MIT © [Ben Drucker](http://bendrucker.me)