Re-add watch command

README.md

@@ -94,6 +94,13 @@ yarn
 yarn build
 ```
 
+Alternatively, to continuously watch the frontend assets and rebuild as necessary:
+
+```
+yarn
+yarn watch
+```
+
 #### Viewing a sample crawl using a Python virtual environment
 
 Run the viewer application using sample data:

esbuild/build.js

@@ -16,10 +16,20 @@ const baseConfig = {
   plugins: [],
 };
 
+const arg = process.argv.slice(2)[0];
+
 (async function () {
   const scriptsConfig = scripts(baseConfig);
   const ctx = await esbuild.context(scriptsConfig);
 
-  await ctx.rebuild();
-  await ctx.dispose();
+  if (arg === 'watch') {
+    const ctx = await esbuild.context(scriptsConfig);
+    await ctx.watch();
+    // Not disposing context here as the user will ctrl+c to end watching.
+  } else {
+    const ctx = await esbuild.context(scriptsConfig);
+    await ctx.rebuild();
+    await ctx.dispose();
+  }
+
 })();

package.json

@@ -10,7 +10,7 @@
     "clean": "rm -rf ./viewer/static/",
     "prettier": "prettier . --check",
     "prettier:fix": "prettier . --write",
-    "watch": "yarn build --watch"
+    "watch": "yarn build watch"
   },
   "dependencies": {
     "@cfpb/cfpb-design-system": "^3.4.9",