clean-css-promise/README.md

clean-css with the default Promise interface and some improvements

# clean-css-promise

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[clean-css](https://github.com/jakubpawlowicz/clean-css) with the default [Promise](https://developer.mozilla.org/docs/Mozilla/JavaScript_code_modules/Promise.jsm/Promise) interface and some improvements

```javascript
const CleanCssPromise = require('clean-css-promise');

(async () => {
  const {styles} = await new CleanCssPromise().minify(`
p {
  color: #ff0000;
}

b {
  /* nothing */
}
`); //=> 'p{color:red}'
})();
```

## Installation

[Use](https://docs.npmjs.com/cli/install) [npm](https://docs.npmjs.com/about-npm/).

```
npm install clean-css-promise
```

## API

```javascript
const CleanCssPromise = require('clean-css-promise');
```

### class CleanCssPromise([*options*])

*options*: `Object` ([clean-css constructor options](https://github.com/jakubpawlowicz/clean-css#constructor-options))  

Almost the same the original `clean-css`, except for:

* [`returnPromise` option](https://github.com/jakubpawlowicz/clean-css#promise-interface) is enabled by default, and cannot be disabled.
* [*onRejected*](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then#Parameters) function receives an `Error` instead of an `Array`.
* All problems that clean-css considers as *warnings*, for example broken CSS syntax, are regarded as *errors*.

```javascript
const CleanCssPromise = require('clean-css-promise');

new CleanCssPromise({})
.minify('@import url(/foo);}')
.catch(err => {
  err.message;
  /*=> `2 errors found while optimizing CSS with clean-css:
  1. Ignoring local @import of "/foo" as resource is missing.
  2. Invalid character(s) '?' at 1:18. Ignoring.

clean-css dangerously ignores these errors but clean-css-promise doesn't, because it's much more reasonable to update the CSS to fix all problems than to pretend that you didn't see the errors.` */
});
```

## License

[ISC License](./LICENSE) © 2017 - 2019 Watanabe Shinnosuke