react-file-previewer/src/utils/setZoomOut.js

A browser/device-agnostic file previewer for PDF and image file types built on top of React-PDF.

import * as R from 'ramda';

const SCALE_FACTOR = 0.25;

/**
 * Reduce the document scale by 25%.
 *
 * @param  {Object} files
 * @return {Object}
 */
const setZoomOut = R.converge(R.assoc('scale'), [
  R.compose(
    R.map(R.subtract(R.__, SCALE_FACTOR)),
    R.when(R.is(Number), R.of),
    R.propOr([1], 'scale'),
  ),
  R.identity,
]);

export default setZoomOut;