Get a list of required polyfill.io features based on browserslist

index.js

const semver = require('semver');
const browserslist = require('browserslist');
const polyFillService = require('polyfill-service');

function browserVersionMatches(browsersListVersion, polyFillServiceVersion)
{
    // Do some quick and easy checks first
    if (browsersListVersion === polyFillServiceVersion) return true;
    if (polyFillServiceVersion === '*') return true;
    if (browsersListVersion === 'all') return true;

    // Otherwise convert the browser version into a semver.
    let version = semver.clean(browsersListVersion, true);
    if (version === null) version = semver.clean(browsersListVersion + '.0.0', true);
    if (version === null) version = semver.clean(browsersListVersion + '.0', true);
    if (version === null) throw new Error(`Could not convert '${browsersListVersion}' into semver`);

    // Then check to see if it satisfies the polyFill range.
    return semver.satisfies(version, polyFillServiceVersion, true);
}

(async () =>
{
    let requirePolyFills = [];
    
    var browsers = browserslist();

    for (let fill of await polyFillService.listAllPolyfills())
    {
        // The Locales add lots of noise, ignore for now
        if (fill.startsWith('Intl')) continue;

        let fillMeta = await polyFillService.describePolyfill(fill);

        if (fillMeta.browsers)
        {
            for (let browser of browsers)
            {
                let segments = browser.split(' ');
                let browserName = segments[0];

                if (fillMeta.browsers[browserName])
                {
                    let browserVersions = segments[1].split('-');

                    for (let browserVersion of browserVersions)
                    {
                        if (browserVersionMatches(browserVersion, fillMeta.browsers[browserName]))
                        {
                            if (requirePolyFills.indexOf(fill) === -1)
                            {
                                requirePolyFills.push(fill);
                            }
                        }
                    }
                }
            }
        }
    }

    console.log(requirePolyFills);

})();