@babel/plugin-proposal-import-defer

Transforms import defer declarations to deferred require() calls.

caution

This plugin can only be used when also compiling modules to CommonJS.

Example

input.js

import defer * as lib from "lib";

later(() => {
  console.log(lib.value);
});

will be transformed to

output.js

"use strict";

function lib(data) {
  lib = () => data;
  return data = _interopRequireWildcard(require("lib"));
}

later(() => {
  console.log(lib().value);
});

Installation

npm

npm install --save-dev @babel/plugin-proposal-import-defer

Yarn

yarn add --dev @babel/plugin-proposal-import-defer

pnpm

pnpm add --save-dev @babel/plugin-proposal-import-defer

Usage

With a configuration file (Recommended)

babel.config.json

{
  "plugins": [
    "@babel/plugin-proposal-import-defer",
    "@babel/plugin-transform-modules-commonjs"
  ]
}

Via CLI

Shell

babel --plugins=@babel/plugin-proposal-import-defer,@babel/plugin-transform-modules-commonjs script.js

Via Node API

JavaScript

require("@babel/core").transformSync("code", {
  plugins: [
    "@babel/plugin-proposal-import-defer",
    "@babel/plugin-transform-modules-commonjs"
  ],
});

References

• Proposal: Deferred Import Evaluation