Perf: Parallelise requests

lib/image.js

@@ -27,13 +27,6 @@ function encodeSvg(content) {
   );
 }
 
-async function reduceAsync(array = [], reducer = (r) => r, initial) {
-  for (const index of array.keys()) {
-    initial = await reducer(initial, array[index]); /* eslint-disable-line no-await-in-loop */
-  }
-
-  return initial;
-}
 
 async function assertSize(resource, maxFileSize, throwError = true) {
   const {mime, contents = ''} = resource || {};
@@ -77,24 +70,22 @@ async function resolve(filepath, {assetPaths, maxFileSize, largeFileCallback, re
   }
 }
 
-function getDataUriMapping(urls = [], options = {}) {
-  return reduceAsync(
-    [...new Set(urls)],
-    async (result, url) => {
-      const file = await resolve(url, options);
-      if (file && file.mime && /image/.test(file.mime)) {
-        result[url] = await getDataUri(file, options);
-      } else if (options.largeFileCallback) {
-        const largeFile = await resolve(url, {...options, maxFileSize: 0});
-        if (largeFile && largeFile.mime && /image/.test(largeFile.mime)) {
-          result[url] = await options.largeFileCallback(largeFile);
-        }
+async function getDataUriMapping(urls = [], options = {}) {
+  const uniqueUrls = [...new Set(urls)];
+  const promises = uniqueUrls.map(async (url) => {
+    const file = await resolve(url, options);
+    if (file && file.mime && /image/.test(file.mime)) {
+      return [url, await getDataUri(file, options)];
+    } else if (options.largeFileCallback) {
+      const largeFile = await resolve(url, {...options, maxFileSize: 0});
+      if (largeFile && largeFile.mime && /image/.test(largeFile.mime)) {
+        return [url, await options.largeFileCallback(largeFile)];
       }
-
-      return result;
-    },
-    {}
-  );
+    }
+    return [url, null];
+  });
+  const results = await Promise.all(promises);
+  return Object.fromEntries(results);
 }
 
 module.exports.getDataUriMapping = getDataUriMapping;