Convert ES6 .js dependencies to ES5 using Typescript transpilation

Question

Convert ES6 .js dependencies to ES5 using Typescript transpilation

In my project, there is a hypothetical Typescript file that I am working with (simplified example).

Utils.ts:

import * as HelperFromNodeModules from 'helper-from-node-modules';

class Utils {
  static foo() {
    return HelperFromNodeModules.parse(...);
  }
}

The helper-from-node-modules import includes a Javascript file.

helper-from-node-modules.js:

const dep = require('foo');
function parse(...) {
   return bar.map((e) => {...});
}

Also included is the index.d.ts from @types/helper-from-node-modules:

export function parse(...);

Within the tsconfig.json, specifically look at:

{
  ...
  "target": "es5",
  "lib": ["es2015.collection","es6", "dom"],
  "sourceMap": true,
  "allowJs": true,
  ...
}

The issue arises when the Typescript compiler combines my compiled source code with all dependencies, resulting in es6 artifacts in the output file even though it should be strictly es5. This causes errors when expecting only es5 javascript.

Is there a way to instruct the Typescript compiler/transpiler to output es5 for javascript dependencies as well?

Additional Info:

Originally, I used react-create-app-typescript and react-scripts-ts as the boilerplate for my React app. The built-in webpack stack has strong opinions on where source code should come from and requires the compiled source to be es5. Any attempt to minify es6 artifacts will cause the minifier/uglifier to crash. Although I can modify the configurations by running npm run-script eject, I prefer to avoid that route and compile the source to es6 without altering their webpack setup.

javascript typescript ecmascript-6 tsconfig create-react-app

Answer 1

Answer №1

Regrettably, there is no straightforward way to convert dependencies from ES6 to ES5. The setting in tsconfig.json specifically pertains to how TypeScript code gets transpiled. Instead, consider utilizing an ES5 version of your helper-from-node-modules. Many libraries like Angular offer various versions such as ES5 (umd), ES5, and ES6. In the library's package.json, you can specify which version to use for TypeScript when packaging with tools like webpack.

If the library lacks support for this feature, your best options are to manually transpile it to ES5 using tools like Babel or seek out an alternative solution. It does seem unusual, though, for a library to solely distribute itself in ES6.

Answer 2

Regrettably, there is no straightforward way to convert dependencies from ES6 to ES5. The setting in tsconfig.json specifically pertains to how TypeScript code gets transpiled. Instead, consider utilizing an ES5 version of your helper-from-node-modules. Many libraries like Angular offer various versions such as ES5 (umd), ES5, and ES6. In the library's package.json, you can specify which version to use for TypeScript when packaging with tools like webpack.

If the library lacks support for this feature, your best options are to manually transpile it to ES5 using tools like Babel or seek out an alternative solution. It does seem unusual, though, for a library to solely distribute itself in ES6.

Answer 3

Answer №2

One interesting approach is to intercept the compilation process and modify your dependencies prior to TypeScript processing using TypeScript transformers.

A transformer essentially involves a function that interacts with the Abstract Syntax Tree (AST) of your program. Here's a simple example:

import * as ts from 'typescript';

export default (program: ts.Program) => {
    return (ctx: ts.TransformationContext) => {
        return (sourceFile: ts.SourceFile) => {
            function visitor(node: ts.Node): ts.Node {
                /**
                 * If this matches the node type you're targeting,
                 * apply necessary changes and return it. Otherwise:
                 */
                return ts.visitEachChild(node, visitor, ctx);
            }

            return ts.visitEachChild(sourceFile, visitor, ctx);
        };
    };
}

If you're working with Webpack, you can integrate this transformer in your build process through the Webpack configuration file.

webpack.config.js

const transformer = require('./your-custom-transformer');

module.exports = {
  /* ... */
  module: {
    rules: [
      {
        test: /\.ts$/,
        loader: 'ts-loader', // (or 'awesome-typescript-loader')
        options: {
          getCustomTransformers: program => ({
            before: [
              transformer(program)
            ]
          })
        }
      }
    ]
  }
};

Answer 4

One interesting approach is to intercept the compilation process and modify your dependencies prior to TypeScript processing using TypeScript transformers.

A transformer essentially involves a function that interacts with the Abstract Syntax Tree (AST) of your program. Here's a simple example:

import * as ts from 'typescript';

export default (program: ts.Program) => {
    return (ctx: ts.TransformationContext) => {
        return (sourceFile: ts.SourceFile) => {
            function visitor(node: ts.Node): ts.Node {
                /**
                 * If this matches the node type you're targeting,
                 * apply necessary changes and return it. Otherwise:
                 */
                return ts.visitEachChild(node, visitor, ctx);
            }

            return ts.visitEachChild(sourceFile, visitor, ctx);
        };
    };
}

If you're working with Webpack, you can integrate this transformer in your build process through the Webpack configuration file.

webpack.config.js

const transformer = require('./your-custom-transformer');

module.exports = {
  /* ... */
  module: {
    rules: [
      {
        test: /\.ts$/,
        loader: 'ts-loader', // (or 'awesome-typescript-loader')
        options: {
          getCustomTransformers: program => ({
            before: [
              transformer(program)
            ]
          })
        }
      }
    ]
  }
};

Answer 5

Answer №3

Encountered this issue while trying to import files into both Next.js and my CLI simultaneously. Next.js has specific automated configurations, so I aimed to align with its requirements to avoid any compatibility issues between Next.js and my CLI.

The solution provided below pertains to the Babel setup. (I referenced https://github.com/vercel/next.js/tree/canary/examples/custom-server-typescript for the tsconfig part.)

Approach to transpile ES6 imports to ES5: (applies outside of nextjs)

Source:

npm install --save-dev @babel/cli @babel/preset-env

Create a .babelrc file:

{
  presets: ["@babel/preset-env"]
}

Add the following to your build script (assuming you already have a package.json script for running npm run build)

To enable JSX functionality (in case there are .tsx files or JSX syntax in .js files):

npm install --save-dev @babel/preset-react

In your .babelrc file:

{
  "presets": [
    "@babel/preset-env",
    [
      "@babel/preset-react",
      {
        "runtime": "automatic"
      }
    ]
  ]
}

To make changes for _app in Next.js, consider adding https://github.com/uiwjs/babel-plugin-transform-remove-imports to eliminate CSS imports.

Answer 6

Encountered this issue while trying to import files into both Next.js and my CLI simultaneously. Next.js has specific automated configurations, so I aimed to align with its requirements to avoid any compatibility issues between Next.js and my CLI.

The solution provided below pertains to the Babel setup. (I referenced https://github.com/vercel/next.js/tree/canary/examples/custom-server-typescript for the tsconfig part.)

Approach to transpile ES6 imports to ES5: (applies outside of nextjs)

Source:

npm install --save-dev @babel/cli @babel/preset-env

Create a .babelrc file:

{
  presets: ["@babel/preset-env"]
}

Add the following to your build script (assuming you already have a package.json script for running npm run build)

To enable JSX functionality (in case there are .tsx files or JSX syntax in .js files):

npm install --save-dev @babel/preset-react

In your .babelrc file:

{
  "presets": [
    "@babel/preset-env",
    [
      "@babel/preset-react",
      {
        "runtime": "automatic"
      }
    ]
  ]
}

To make changes for _app in Next.js, consider adding https://github.com/uiwjs/babel-plugin-transform-remove-imports to eliminate CSS imports.

Convert ES6 .js dependencies to ES5 using Typescript transpilation

Answer №1

Answer №2

Answer №3

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