feat: support command line pass in esbuild configuration

README.md

@@ -20,6 +20,12 @@ node -r esbuild-register file.ts
 
 It will use `jsxFactory`, `jsxFragmentFactory` and `target` options from your `tsconfig.json`
 
+You can also pass a JSON string to specify configuration options for esbuild, such as if I want to pass in the banner configuration.
+
+```bash
+node -r esbuild-register file.ts --esbuild-config="{\"banner\": \"console.log('is banner')\"}"
+```
+
 ### Experimental loader support
 
 When using in a project with `type: "module"` in `package.json`, you need the `--loader` flag to load TypeScript files:

register.js

@@ -1,3 +1,46 @@
+const ESBUILD_CONFIG_NAME = '--esbuild-config'
+
+// parse process.argv.slice(2) and return an object
+const parseArgs = (argv) => {
+  const args = {}
+  argv.forEach(arg => {
+    const index = arg.indexOf('=')
+    if (index !== -1) {
+      const key = arg.slice(0, index)
+      const value = arg.slice(index + 1)
+      args[key] = value
+    }
+  })
+  return args
+}
+
+const args = parseArgs(process.argv.slice(2));
+
+// Determine if a string is json
+const isJson = (str) => {
+  let result;
+  try {
+    result = JSON.parse(str);
+  } catch (e) {
+    return false;
+  }
+  if (typeof result !== 'object' || Array.isArray(result) || result === null) {
+    return false;
+  }
+  return result;
+}
+
+let isJsonConfig;
+
+if (typeof args[ESBUILD_CONFIG_NAME] === 'string') {
+  isJsonConfig = isJson(args[ESBUILD_CONFIG_NAME]);
+  if (!isJsonConfig) {
+    // not json
+    console.log('esbuild-config is not json');
+  }
+}
+
 require('./dist/node.js').register({
   target: `node${process.version.slice(1)}`,
+  ...(isJsonConfig || {}),
 })