DefinitelyTyped/types/react-cropper/react-cropper-tests.tsx

import * as React from 'react';
import Cropper from 'react-cropper';
// If you choose not to use import, you need to assign Cropper to default
// var Cropper = require('react-cropper').default

class Demo extends React.Component {
    crop() {
        // image in dataUrl
        console.log((this.refs['cropper'] as any).getCroppedCanvas().toDataURL());
    }

    render() {
        return (
            <Cropper
                ref='cropper'
                src='http://fengyuanchen.github.io/cropper/img/picture.jpg'
                style={{ height: 400, width: '100%' }}
                // Cropper.js options
                aspectRatio={16 / 9}
                guides={false}
                crop={this.crop.bind(this) } />
        );
    }
}

function testCropperRef() {
    const refIsWorking = <Cropper
        ref={(el: Cropper) => {
            // $ExpectError el can be null
            el.getCroppedCanvas();
            if (el !== null) {
                // el is a cropperjs element
                el.getCroppedCanvas();
                // el is also a React.Component instance
                el.props;
            }
        }}
    />;

    const refIsOptional = <Cropper />;
}