diff --git a/web/src/portico/team.js b/web/src/portico/team.ts
similarity index 67%
rename from web/src/portico/team.js
rename to web/src/portico/team.ts
index d5deb81272..3580f931a1 100644
--- a/web/src/portico/team.js
+++ b/web/src/portico/team.ts
@@ -1,7 +1,26 @@
 import $ from "jquery";
 import _ from "lodash";
 
-const repo_name_to_tab_name = {
+// The list of repository names is duplicated here in order to provide
+// a clear type for Contributor objects.
+//
+// TODO: We can avoid this if we introduce a `contributions` object
+// referenced from Contributor, rather than having repository names be
+// direct keys in the namespace that also has `email`.
+const all_repository_names = [
+    "zulip",
+    "zulip-desktop",
+    "zulip-mobile",
+    "python-zulip-api",
+    "zulip-js",
+    "zulipbot",
+    "zulip-terminal",
+    "zulip-ios-legacy",
+    "zulip-android",
+] as const;
+type RepositoryName = (typeof all_repository_names)[number];
+
+const repo_name_to_tab_name: Record<RepositoryName, string> = {
     zulip: "server",
     "zulip-desktop": "desktop",
     "zulip-mobile": "mobile",
@@ -13,26 +32,36 @@ const repo_name_to_tab_name = {
     "zulip-android": "",
 };
 
+export type Contributor = {
+    avatar: string;
+    email?: string;
+    github_username?: string;
+    name: string;
+} & {
+    [K in RepositoryName]?: number;
+};
+
 // Remember the loaded repositories so that HTML is not redundantly edited
 // if a user leaves and then revisits the same tab.
-const loaded_repos = [];
+const loaded_repos: string[] = [];
 
-function calculate_total_commits(contributor) {
+function calculate_total_commits(contributor: Contributor): number {
     let commits = 0;
-    for (const repo_name of Object.keys(repo_name_to_tab_name)) {
+    for (const repo_name of all_repository_names) {
         commits += contributor[repo_name] || 0;
     }
     return commits;
 }
 
-function get_profile_url(contributor, tab_name) {
-    const commit_email_linked_to_github = "github_username" in contributor;
-
-    if (commit_email_linked_to_github) {
-        return "https://github.com/" + contributor.github_username;
+function get_profile_url(contributor: Contributor, tab_name?: string): string | undefined {
+    if (contributor.github_username) {
+        return `https://github.com/${contributor.github_username}`;
     }
 
     const email = contributor.email;
+    if (!email) {
+        return undefined;
+    }
 
     if (tab_name) {
         return `https://github.com/zulip/${tab_name}/commits?author=${email}`;
@@ -47,21 +76,21 @@ function get_profile_url(contributor, tab_name) {
     return undefined;
 }
 
-function get_display_name(contributor) {
+function get_display_name(contributor: Contributor): string {
     if (contributor.github_username) {
         return "@" + contributor.github_username;
     }
     return contributor.name;
 }
 
-function exclude_bot_contributors(contributor) {
+function exclude_bot_contributors(contributor: Contributor): boolean {
     return contributor.github_username !== "dependabot[bot]";
 }
 
 // TODO (for v2 of /team/ contributors):
 //   - Make tab header responsive.
 //   - Display full name instead of GitHub username.
-export default function render_tabs(contributors) {
+export default function render_tabs(contributors: Contributor[]): void {
     const template = _.template($("#contributors-template").html());
     const count_template = _.template($("#count-template").html());
     const total_count_template = _.template($("#total-count-template").html());
@@ -93,7 +122,7 @@ export default function render_tabs(contributors) {
         }),
     );
 
-    for (const repo_name of Object.keys(repo_name_to_tab_name)) {
+    for (const repo_name of all_repository_names) {
         const tab_name = repo_name_to_tab_name[repo_name];
         if (!tab_name) {
             continue;
@@ -103,11 +132,13 @@ export default function render_tabs(contributors) {
 
         $(`#${CSS.escape(tab_name)}`).on("click", () => {
             if (!loaded_repos.includes(repo_name)) {
-                const filtered_by_repo = contributors_list.filter((c) => c[repo_name]);
+                const filtered_by_repo = contributors_list.filter((c) => c[repo_name] || 0);
                 const html = filtered_by_repo
-                    .sort((a, b) =>
-                        a[repo_name] < b[repo_name] ? 1 : a[repo_name] > b[repo_name] ? -1 : 0,
-                    )
+                    .sort((a, b) => {
+                        const a_commits = a[repo_name] || 0;
+                        const b_commits = b[repo_name] || 0;
+                        return a_commits < b_commits ? 1 : a_commits > b_commits ? -1 : 0;
+                    })
                     .map((c) =>
                         template({
                             name: get_display_name(c),
@@ -121,9 +152,10 @@ export default function render_tabs(contributors) {
 
                 $(`#tab-${CSS.escape(tab_name)} .contributors-grid`).html(html);
                 const contributor_count = filtered_by_repo.length;
-                const hundred_plus_contributor_count = filtered_by_repo.filter(
-                    (c) => c[repo_name] >= 100,
-                ).length;
+                const hundred_plus_contributor_count = filtered_by_repo.filter((c) => {
+                    const commits = c[repo_name] || 0;
+                    return commits >= 100;
+                }).length;
                 const repo_url = `https://github.com/zulip/${repo_name}`;
                 $(`#tab-${CSS.escape(tab_name)}`).prepend(
                     count_template({