AWS Lambda@Edge whitelisted image to webp request mapper

lambda-img-to-webp.js

'use strict';

const whitelist = {
    '/static/img/photo.jpg': '/static/img/photo.webp'
};

exports.handler = (event, context, callback) => {

    // Grab HTTP request and it's headers
    const request = event.Records[0].cf.request;
    const headers = request.headers;

    // Detect WebP support and see if the file is whitelisted
    const supportsWebp = /.*(image\/webp).*/.test(headers.Accept);
    const isWhitelisted = !!whitelist[request.uri];

    if (supportsWebp && isWhitelisted) {
        request.uri = whitelist[request.uri];
    }

    return callback(null, request);
};