koganei/import-map-generation.md

## import-map-generation.md

      
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              import-map-generation.md
            
          
    USER

Hi, can you give me the javascript code that will generate an import map for a given package.json so that code works in web browsers without any kind of building?
ASSISTANT

Certainly! Below is a JavaScript code snippet that generates an import map for a given package.json file. This code assumes that the dependencies in the package.json are already downloaded and placed in a folder named node_modules within your project directory, and it generates an import map compatible with native ES modules in web browsers without requiring a build step.
const fs = require("fs");

function generateImportMap(packageJsonPath) {
  const packageJsonContent = fs.readFileSync(packageJsonPath, "utf-8");
  const packageJson = JSON.parse(packageJsonContent);

  if (!packageJson.dependencies) {
    console.error("No dependencies found in package.json");
    return;
  }

  const importMap = {
    imports: {},
  };

  for (const [packageName, packageVersion] of Object.entries(packageJson.dependencies)) {
    const packagePath = `./node_modules/${packageName}/package.json`;
    const packageContent = fs.readFileSync(packagePath, "utf-8");
    const packageData = JSON.parse(packageContent);

    if (!packageData.module) {
      console.error(`The package ${packageName} does not have a module entry.`);
      continue;
    }

    const modulePath = `./node_modules/${packageName}/${packageData.module}`;
    importMap.imports[packageName] = modulePath;
  }

  fs.writeFileSync("import-map.json", JSON.stringify(importMap, null, 2), "utf-8");
  console.log("Import map has been generated: import-map.json");
}

// Replace the path below with the path to your package.json file
generateImportMap("./path/to/your/package.json");
To use this script, create a file named generate-import-map.js in your project directory and paste the code above into the file. Replace ./path/to/your/package.json with the path to your package.json file. Then, run the script using Node.js:
node generate-import-map.js
The script will generate an import-map.json file in the project directory. To use the import map in your HTML file, add the following code within the <head> tag:
<script type="importmap" src="import-map.json"></script>
Now, you can use the native ES modules in your JavaScript code, importing packages directly from your node_modules folder:
import { functionName } from "package-name";