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/Babel 7

@babel/plugin-proposal-async-do-expressions

The async do { .. } expression executes a block (with one or many statements in it) in an asynchronous context, and the final statement completion value inside the block becomes the completion value of the asynchronous code.

Example​

Issuing HTTP request in parallel

Promise.all([
  async do {
    const result = await fetch('https://example.com/A');
    await result.json()
  },
  async do {
    const result = await fetch('https://example.org/B');
    await result.json()
  },
]).then(([a, b]) => {
  console.log("example.com/A", a);
  console.log("example.org/B", b);
})

will be transformed to

Promise.all([
  (async () {
    const result = await fetch('https://example.com/A');
    return await result.json()
  })(),
  (async () {
    const result = await fetch('https://example.org/B');
    return await result.json()
  })(),
]).then(([a, b]) => {
  console.log("example.com/A", a);
  console.log("example.org/B", b);
})

Installation​

  • npm
  • Yarn
  • pnpm
npm install --save-dev @babel/plugin-proposal-async-do-expressions

Usage​ 

{
  "plugins": ["@babel/plugin-proposal-async-do-expressions"]
}

Note: This plugin transpiles async do {} to ES2017 Async arrow function async () => {}. If you target to an older engine, i.e. Node.js 6 or IE 11, please also add @babel/plugin-transform-async-to-generator:

{
  "plugins": [
    "@babel/plugin-proposal-async-do-expressions",
    "@babel/plugin-transform-async-to-generator"
  ]
}

Via CLI​ 

babel --plugins @babel/plugin-proposal-async-do-expressions script.js

Via Node API​ 

require("@babel/core").transformSync("code", {
  plugins: ["@babel/plugin-proposal-async-do-expressions"],
});

References​

© 2014-present Sebastian McKenzie
Licensed under the MIT License.
https://babeljs.io/docs/babel-plugin-proposal-async-do-expressions/