Demonstrate more javascript backend functionality

.gitignore

@@ -4,3 +4,7 @@
 /.pids
 /.pants.workdir.file_lock*
 
+node_modules
+
+# Build output when build invoked with `npm run build`
+dist_npm

.prettierrc.yaml

@@ -0,0 +1,3 @@
+# Example prettier config - try changing this and running `pants fmt ::`
+# See https://prettier.io/docs/en/configuration.html for more options
+singleQuote: true

BUILD

@@ -1 +1,15 @@
-package_json(name="hello_pkg")
+package_json(
+    name="hello_pkg",
+    scripts=[
+        node_test_script(
+            coverage_args=["--coverage", "--coverage-directory=.coverage/"],
+            coverage_output_files=[".coverage/lcov-report/index.html"],
+            coverage_output_directories=[".coverage/lcov-report"],
+        ),
+        node_build_script(
+            entry_point="build",
+            extra_env_vars=["FOO=BAR"],
+            output_files=["dist_npm/index.js"],
+        ),
+    ],
+)

README.md

@@ -17,6 +17,32 @@ Try these out in this repo.
 
 ```
 pants dependencies src/index.js
+pants dependencies --transitive src/index.js
+```
+
+## Lint and format
+
+```
+pants lint ::
+pants fmt ::
+```
+
+## Test
+
+```
+pants test ::
+pants test --use-coverage ::
+```
+
+The example is configured to use Jest as the test runner via `package.json` "scripts.test" key.
+Mocha is also supported by the Javascript backend.
+
+## Package
+
+The example uses esbuild to package the source into a single file in the `dist` directory.
+
+```
+pants package ::
 ```
 
 ## Generate lockfiles