如何将TypeScript项目中的ES6 JS依赖转译为ES5？

Got it, let's break down how to get that ES6-based helper-from-node-modules dependency working with your ES5-targeted TypeScript setup. Here are the most reliable approaches:

Option 1: Use Babel with a Bundler (Webpack Example) #

If you're using a bundler like Webpack, you can configure Babel to transpile the specific dependency alongside your TypeScript code.

Step 1: Install Required Packages #

First, add Babel and its presets:

npm install --save-dev @babel/core @babel/preset-env babel-loader

Step 2: Configure Babel #

Create a .babelrc file in your project root:

{
  "presets": [
    ["@babel/preset-env", {
      "targets": {
        "browsers": "> 0.25%, not dead",
        "node": "10"
      },
      "modules": false
    }]
  ]
}

Step 3: Update Webpack Config #

Modify your webpack.config.js to include babel-loader and explicitly process the helper-from-node-modules package (since bundlers often skip node_modules by default):

module.exports = {
  // ... other existing config
  module: {
    rules: [
      // TypeScript loader first
      {
        test: /\.tsx?$/,
        use: 'ts-loader',
        exclude: /node_modules/
      },
      // Babel loader for the ES6 dependency
      {
        test: /\.js$/,
        include: /node_modules\/helper-from-node-modules/,
        use: 'babel-loader'
      }
    ]
  }
};

Option 2: Configure TypeScript to Transpile the Dependency #

TypeScript can transpile JavaScript files directly if you adjust your tsconfig.json settings. This works well if the dependency's ES6 syntax is limited to features TS can convert to ES5.

Update tsconfig.json #

Add these settings to your config:

{
  "compilerOptions": {
    "target": "ES5",
    "allowJs": true,
    "checkJs": false, // Optional: Disable if you don't want TS to type-check the dependency's JS
    "lib": ["ES6", "DOM"] // Include ES6 lib to support syntax during transpilation
  },
  "include": [
    "src/**/*",
    "node_modules/helper-from-node-modules/**/*.js" // Explicitly include the dependency
  ]
}

Option 3: Pre-Transpile the Dependency Locally #

If you don't want to adjust your build pipeline, you can manually transpile the dependency and use the transpiled version:

1. Clone the helper-from-node-modules repository locally
2. Transpile it with Babel:

   npx babel src --out-dir dist --presets @babel/preset-env
   

3. Replace the npm package in your package.json with the local transpiled version:

   "dependencies": {
     "helper-from-node-modules": "file:../path/to/transpiled-helper"
   }
   

Key Notes #

• Ensure your tsconfig.json's target is set to ES5 to guarantee your own TypeScript code is transpiled correctly.
• The @types/helper-from-node-modules typings will work seamlessly with any of these approaches—they only describe the API, not the underlying implementation.

内容的提问来源于stack exchange，提问作者Samuel Davidson