Updated @deephaven/jsapi-nodejs README to reflect latest api (DH-19067)

Author: bmingles

packages/jsapi-nodejs/README.md

@@ -1,8 +1,7 @@
 # @deephaven/jsapi-nodejs
 
 Deephaven utils for consuming Jsapi from a server from a nodejs app. It can 
-optionally convert the server module format from `ESM` -> `CJS` or `CJS` -> `ESM` 
-if the server and consumer don't use the same module format.
+provide the api as a `CJS` or `ESM` module.
 
 ## Install
 
@@ -12,21 +11,57 @@ npm install --save @deephaven/jsapi-nodejs
 
 ## Usage
 
+### Download jsapi as `ESM` Module
+
 ```typescript
 import fs from 'node:fs';
 import path from 'node:path';
+import type { dh as DhType } from '@deephaven/jsapi-types'
 
 import { loadModules } from '@deephaven/jsapi-nodejs';
 
 const tmpDir = path.join(__dirname, 'tmp');
 
-// Download jsapi `ESM` files from DH Community server and export as `CJS` module.
-const dhc = await loadModules({
+const dhc = (
+  await loadModules<{ default: typeof DhType }>({
+    serverUrl: new URL('http://localhost:10000'),
+    serverPaths: ['jsapi/dh-core.js', 'jsapi/dh-internal.js'],
+    storageDir: tmpDir,
+    targetModuleType: 'esm',
+    download: true,
+  })
+).default; // The dh instance will be exported on the .default property
+```
+
+### Download jsapi as `CJS` Module
+
+```typescript
+const dhc = await loadModules<typeof DhType>({
   serverUrl: new URL('http://localhost:10000'),
   serverPaths: ['jsapi/dh-core.js', 'jsapi/dh-internal.js'],
-  download: true,
   storageDir: tmpDir,
-  sourceModuleType: 'esm',
   targetModuleType: 'cjs',
+  // Provide a post-download transformation callback. The jsapi is an `ESM`
+  // module on the server, so we have to replace some things to make it `CJS`
+  // compliant.
+  download: (serverPath, content) => {
+    if (serverPath === 'jsapi/dh-core.js') {
+      return content
+        .replace(
+          `import {dhinternal} from './dh-internal.js';`,
+          `const {dhinternal} = require("./dh-internal.js");`,
+        )
+        .replace(`export default dh;`, `module.exports = dh;`)
+    }
+
+    if (serverPath === 'jsapi/dh-internal.js') {
+      return content.replace(
+        `export{__webpack_exports__dhinternal as dhinternal};`,
+        `module.exports={dhinternal:__webpack_exports__dhinternal};`,
+      )
+    }
+
+    return content
+  }
 });
 ```