jsenv · dmail · May 30, 2025 · May 30, 2025 · May 30, 2025
diff --git a/package.json b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@jsenv/importmap-node-module",
-  "version": "7.1.1",
+  "version": "7.2.0",
   "description": "Generate importmap for node_modules",
   "license": "MIT",
   "repository": {

diff --git a/src/cli.mjs b/src/cli.mjs
@@ -39,9 +39,10 @@ if (positionals.length > 1) {
 if (
   !outfile.endsWith(".html") &&
   !outfile.endsWith(".importmap") &&
-  !outfile.endsWith(".json")
+  !outfile.endsWith(".json") &&
+  !outfile.endsWith(".js")
 ) {
-  console.error("Error: outfile must end with .html, .importmap or .json");
+  console.error("Error: outfile must end with .html, .importmap, .json or .js");
   process.exit(1);
 }
 

diff --git a/src/step_write_into_files/write_into_files.js b/src/step_write_into_files/write_into_files.js
@@ -22,13 +22,19 @@ export const writeIntoFiles = (
     const importmapAsJson = JSON.stringify(importmap, null, "  ");
     if (fileUrl.endsWith(".html")) {
       writeIntoHtmlFile(fileUrl, importmapAsJson, { logger });
+    } else if (fileUrl.endsWith(".js")) {
+      writeInfoJsFile(fileUrl, importmapAsJson, { logger });
     } else {
-      writeFileSync(fileUrl, importmapAsJson);
-      logger.info(`-> ${urlToFileSystemPath(fileUrl)}`);
+      writeIntoJsonFile(fileUrl, importmapAsJson, { logger });
     }
   }
 };
 
+const writeIntoJsonFile = (jsonFileUrl, importmapAsJson, { logger }) => {
+  writeFileSync(jsonFileUrl, importmapAsJson);
+  logger.info(`-> ${urlToFileSystemPath(jsonFileUrl)}`);
+};
+
 const writeIntoHtmlFile = (htmlFileUrl, importmapAsJson, { logger }) => {
   const htmlAst = parseHtml({
     html: readFileSync(htmlFileUrl, { as: "string" }),
@@ -80,3 +86,38 @@ const writeIntoHtmlFile = (htmlFileUrl, importmapAsJson, { logger }) => {
   const html = stringifyHtmlAst(htmlAst);
   writeFileSync(new URL(htmlFileUrl), html);
 };
+
+const writeInfoJsFile = (jsFileUrl, importmapAsJson, { logger }) => {
+  const jsFileContent = `
+const currentScript = document.currentScript;
+if (!currentScript) {
+  throw new Error(
+    "document.currentScript is not available, cannot inject importmap"
+  );
+}
+const baseUrl = new URL(".", currentScript.src).href;
+const importmap = ${importmapAsJson};
+const topLevelMappings = importmap.imports;
+const scopedMappings = importmap.scopes;
+const makeMappingsAbsolute = () => {
+  for (const key of Object.keys(mappings)) {
+    mappings[key] = baseUrl + mappings[key];
+  }
+}
+if (topLevelMappings) {
+  makeMappingsAbsolute(topLevelMappings);
+}
+if (scopedMappings) {
+  for (const scope of Object.keys(scopedMappings)) {
+    const mappings = scopedMappings[scope];
+    makeMappingsAbsolute(mappings);
+  }
+}
+const importmapScript = document.createElement("script");
+importmapScript.type = "importmap";
+importmapScript.textContent = importmap;
+currentScript.after(importmapScript);
+`;
+  writeFileSync(jsFileUrl, jsFileContent);
+  logger.info(`-> ${urlToFileSystemPath(jsFileUrl)}`);
+};
diff --git a/tests/write_inside_js/_write_inside_js.test.mjs/0_basic/0_basic.md b/tests/write_inside_js/_write_inside_js.test.mjs/0_basic/0_basic.md
@@ -0,0 +1,92 @@
+# [0_basic](../../write_inside_js.test.mjs#L21)
+
+```js
+run("0_basic")
+```
+
+# 1/2 write 6 files into "./git_ignored/"
+
+## node_modules/foo/foo.js
+```js
+console.log('foo');
+```
+
+## node_modules/foo/package.json
+```json
+{
+  "name": "foo",
+  "main": "./foo.js",
+  "private": true
+}
+```
+
+## index.html
+```html
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Title</title>
+    <meta charset="utf-8">
+    <link rel="icon" href="data:,">
+  </head>
+
+  <body>
+    <script type="module" src="./main.js"></script>
+  </body>
+</html>
+```
+
+## main.js
+```js
+import "foo";
+
+```
+
+## package.json
+```json
+{
+  "name": "root",
+  "private": true,
+  "dependencies": {
+    "foo": "*"
+  }
+}
+```
+
+## index.js
+
+```
+
+const currentScript = document.currentScript;
+if (!currentScript) {
+  throw new Error(
+    "document.currentScript is not available, cannot inject importmap"
+  );
+}
+const baseUrl = new URL(".", currentScript.src).href;
+const importmap = {
+  "imports": {
+    "root/": "./",
+    "foo/": "./node_modules/foo/",
+    "root": "./index",
+    "foo": "./node_modules/foo/foo.js"
+  },
+  "scopes": {}
+};
+const topLevelMappings = importmap.imports;
+const scopedMappings = importmap.scopes;
+const makeMappingsAbsolute = () => {
+```
+see [git_ignored/index.js](git_ignored/index.js) for more
+
+# 2/2 resolve
+
+```js
+undefined
+```
+
+---
+
+<sub>
+  Generated by <a href="https://github.com/jsenv/core/tree/main/packages/independent/snapshot">@jsenv/snapshot</a>
+</sub>
diff --git a/tests/write_inside_js/_write_inside_js.test.mjs/write_inside_js.test.mjs.md b/tests/write_inside_js/_write_inside_js.test.mjs/write_inside_js.test.mjs.md
@@ -0,0 +1,10 @@
+# [write_inside_js.test.mjs](../write_inside_js.test.mjs)
+
+
+- [0_basic](0_basic/0_basic.md)
+
+---
+
+<sub>
+  Generated by <a href="https://github.com/jsenv/core/tree/main/packages/independent/snapshot">@jsenv/snapshot</a>
+</sub>
diff --git a/tests/write_inside_js/fixtures/0_basic/index.html b/tests/write_inside_js/fixtures/0_basic/index.html
@@ -0,0 +1,12 @@
+<!doctype html>
+<html>
+  <head>
+    <title>Title</title>
+    <meta charset="utf-8" />
+    <link rel="icon" href="data:," />
+  </head>
+
+  <body>
+    <script type="module" src="./main.js"></script>
+  </body>
+</html>
diff --git a/tests/write_inside_js/fixtures/0_basic/main.js b/tests/write_inside_js/fixtures/0_basic/main.js
@@ -0,0 +1 @@
+import "foo";
diff --git a/tests/write_inside_js/fixtures/0_basic/node_modules/foo/foo.js b/tests/write_inside_js/fixtures/0_basic/node_modules/foo/foo.js
diff --git a/tests/write_inside_js/fixtures/0_basic/node_modules/foo/package.json b/tests/write_inside_js/fixtures/0_basic/node_modules/foo/package.json
diff --git a/tests/write_inside_js/fixtures/0_basic/package.json b/tests/write_inside_js/fixtures/0_basic/package.json
@@ -0,0 +1,7 @@
+{
+  "name": "root",
+  "private": true,
+  "dependencies": {
+    "foo": "*"
+  }
+}
diff --git a/tests/write_inside_js/write_inside_js.test.mjs b/tests/write_inside_js/write_inside_js.test.mjs
@@ -0,0 +1,22 @@
+import { replaceFileStructureSync } from "@jsenv/filesystem";
+import { writeImportmaps } from "@jsenv/importmap-node-module";
+import { snapshotWriteImportmaps } from "@jsenv/importmap-node-module/tests/snapshot_write_importmaps.js";
+
+const run = async (scenario, options) => {
+  replaceFileStructureSync({
+    from: new URL(`./fixtures/${scenario}/`, import.meta.url),
+    to: new URL("./git_ignored/", import.meta.url),
+  });
+  await writeImportmaps({
+    logLevel: "warn",
+    directoryUrl: new URL("./git_ignored/", import.meta.url),
+    importmaps: {
+      "index.js": {},
+    },
+    ...options,
+  });
+};
+
+await snapshotWriteImportmaps(import.meta.url, ({ test }) => {
+  test("0_basic", () => run("0_basic"));
+});