Closes #2923: Remove moment.js from reader view web extension

components/feature/readerview/src/main/assets/extensions/readerview/manifest.json

@@ -5,7 +5,7 @@
   "content_scripts": [
     {
       "matches": ["*://*/*"],
-      "js": ["readability/readability-0.2.0.js", "readability/readability-readerable-0.2.0.js", "moment/moment-2.24.0.js", "readerview.js"],
+      "js": ["readability/readability-0.2.0.js", "readability/readability-readerable-0.2.0.js", "readerview.js"],
       "css": ["readerview.css"],
       "run_at": "document_idle"
     }

components/feature/readerview/src/main/assets/extensions/readerview/readerview.js

@@ -191,15 +191,23 @@ class ReaderView {
     const readingTimeMinsSlow = Math.ceil(length / charactersPerMinuteLow);
     const readingTimeMinsFast  = Math.ceil(length / charactersPerMinuteHigh);
 
-    // TODO remove moment.js: https://github.com/mozilla-mobile/android-components/issues/2923
-    // We only want to show minutes and not have it converted to hours.
-    moment.relativeTimeThreshold('m', Number.MAX_SAFE_INTEGER);
-
-    if (readingTimeMinsSlow == readingTimeMinsFast) {
-      return moment.duration(readingTimeMinsFast, 'minutes').locale(lang).humanize();
+    // Construct a localized and "humanized" reading time in minutes.
+    // If we have both a fast and slow reading time we'll show both e.g.
+    // "2 - 4 minutes", otherwise we'll just show "4 minutes".
+    var parts = new Intl.RelativeTimeFormat(lang).formatToParts(readingTimeMinsSlow, 'minute');
+
+    if (parts.length == 3) {
+      // No need to use part[0] which represents the literal "in".
+      var readingTime = parts[1].value; // reading time in minutes
+      var minutesLiteral = parts[2].value; // localized singular or plural literal of 'minute'
+      var readingTimeString = `${readingTime} ${minutesLiteral}`;
+      if (readingTimeMinsSlow != readingTimeMinsFast) {
+        readingTimeString = `${readingTimeMinsFast} - ${readingTimeString}`;
+      }
+      return readingTimeString;
     }
 
-    return `${readingTimeMinsFast} - ${moment.duration(readingTimeMinsSlow, 'minutes').locale(lang).humanize()}`;
+    return "";
   }
 
   /**