# decamelize [](https://travis-ci.org/sindresorhus/decamelize) > Convert a camelized string into a lowercased one with a custom separator
> Example: `unicornRainbow` → `unicorn_rainbow` ## Install ``` $ npm install --save decamelize ``` ## Usage ```js const decamelize = require('decamelize'); decamelize('unicornRainbow'); //=> 'unicorn_rainbow' decamelize('unicornRainbow', '-'); //=> 'unicorn-rainbow' ``` ## API ### decamelize(input, [separator]) #### input Type: `string` #### separator Type: `string`
Default: `_` ## Related See [`camelcase`](https://github.com/sindresorhus/camelcase) for the inverse. ## License MIT © [Sindre Sorhus](https://sindresorhus.com)