diff --git a/src/content-helpers.js b/src/content-helpers.ts
similarity index 86%
rename from src/content-helpers.js
rename to src/content-helpers.ts
index c82f808c5..061073c5e 100644
--- a/src/content-helpers.js
+++ b/src/content-helpers.ts
@@ -1,6 +1,6 @@
 /*
 Copyright 2018 New Vector Ltd
-Copyright 2019 The Matrix.org Foundation C.I.C.
+Copyright 2018 - 2021 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -23,7 +23,7 @@ limitations under the License.
  * @param {string} htmlBody the HTML representation of the message
  * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
  */
-export function makeHtmlMessage(body, htmlBody) {
+export function makeHtmlMessage(body: string, htmlBody: string) {
     return {
         msgtype: "m.text",
         format: "org.matrix.custom.html",
@@ -38,7 +38,7 @@ export function makeHtmlMessage(body, htmlBody) {
  * @param {string} htmlBody the HTML representation of the notice
  * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
  */
-export function makeHtmlNotice(body, htmlBody) {
+export function makeHtmlNotice(body: string, htmlBody: string) {
     return {
         msgtype: "m.notice",
         format: "org.matrix.custom.html",
@@ -53,7 +53,7 @@ export function makeHtmlNotice(body, htmlBody) {
  * @param {string} htmlBody the HTML representation of the emote
  * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
  */
-export function makeHtmlEmote(body, htmlBody) {
+export function makeHtmlEmote(body: string, htmlBody: string) {
     return {
         msgtype: "m.emote",
         format: "org.matrix.custom.html",
@@ -67,7 +67,7 @@ export function makeHtmlEmote(body, htmlBody) {
  * @param {string} body the plaintext body of the emote
  * @returns {{msgtype: string, body: string}}
  */
-export function makeTextMessage(body) {
+export function makeTextMessage(body: string) {
     return {
         msgtype: "m.text",
         body: body,
@@ -79,7 +79,7 @@ export function makeTextMessage(body) {
  * @param {string} body the plaintext body of the notice
  * @returns {{msgtype: string, body: string}}
  */
-export function makeNotice(body) {
+export function makeNotice(body: string) {
     return {
         msgtype: "m.notice",
         body: body,
@@ -91,7 +91,7 @@ export function makeNotice(body) {
  * @param {string} body the plaintext body of the emote
  * @returns {{msgtype: string, body: string}}
  */
-export function makeEmoteMessage(body) {
+export function makeEmoteMessage(body: string) {
     return {
         msgtype: "m.emote",
         body: body,
diff --git a/src/content-repo.js b/src/content-repo.ts
similarity index 79%
rename from src/content-repo.js
rename to src/content-repo.ts
index 1b92d59ae..baa91879b 100644
--- a/src/content-repo.js
+++ b/src/content-repo.ts
@@ -1,6 +1,5 @@
 /*
-Copyright 2015, 2016 OpenMarket Ltd
-Copyright 2019 The Matrix.org Foundation C.I.C.
+Copyright 2015 - 2021 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -34,8 +33,14 @@ import * as utils from "./utils";
  * for such URLs.
  * @return {string} The complete URL to the content.
  */
-export function getHttpUriForMxc(baseUrl, mxc, width, height,
-                           resizeMethod, allowDirectLinks) {
+export function getHttpUriForMxc(
+    baseUrl: string,
+    mxc: string,
+    width: number,
+    height: number,
+    resizeMethod: string,
+    allowDirectLinks: boolean,
+): string {
     if (typeof mxc !== "string" || !mxc) {
         return '';
     }
@@ -51,13 +56,13 @@ export function getHttpUriForMxc(baseUrl, mxc, width, height,
     const params = {};
 
     if (width) {
-        params.width = Math.round(width);
+        params["width"] = Math.round(width);
     }
     if (height) {
-        params.height = Math.round(height);
+        params["height"] = Math.round(height);
     }
     if (resizeMethod) {
-        params.method = resizeMethod;
+        params["method"] = resizeMethod;
     }
     if (Object.keys(params).length > 0) {
         // these are thumbnailing params so they probably want the
@@ -71,7 +76,7 @@ export function getHttpUriForMxc(baseUrl, mxc, width, height,
         fragment = serverAndMediaId.substr(fragmentOffset);
         serverAndMediaId = serverAndMediaId.substr(0, fragmentOffset);
     }
-    return baseUrl + prefix + serverAndMediaId +
-        (Object.keys(params).length === 0 ? "" :
-        ("?" + utils.encodeParams(params))) + fragment;
+
+    const urlParams = (Object.keys(params).length === 0 ? "" : ("?" + utils.encodeParams(params)));
+    return baseUrl + prefix + serverAndMediaId + urlParams + fragment;
 }