fast-async

6.3.8 verified Sat Apr 25 auth: no javascript

A Babel plugin that transforms ES7 async/await to Promise-based code without generators, offering 3-4x performance improvement in browsers vs Babel's default regenerator approach. Current stable version is 6.3.8 (for Babel 6) and version 7 for Babel 7 (beta). Uses the nodent library under the hood. Key differentiators: avoids generators and regenerator, supports 'spec' mode for spec-compliance, and allows runtime pattern customization. Has undergone several fixes for edge cases like destructuring and export hoisting.

Common errors

error Error: Couldn't find preset "es2015" relative to directory ... ↓

cause Missing Babel presets required by fast-async or configuration error

fix

Ensure babel-preset-es2015 (or equivalent) is installed and listed in .babelrc 'presets'.

error TypeError: Cannot read property 'async' of undefined ↓

cause Plugin loaded incorrectly or Babel version mismatch (e.g., using v6 plugin with Babel 7)

fix

Verify Babel version and install correct fast-async version (v6 for Babel 6, v7 for Babel 7).

error SyntaxError: Unexpected token (1:14) ... while parsing async function ↓

cause Babel parser does not support certain async/await syntax edge cases (e.g., await in non-async function)

fix

Ensure all await expressions are inside async functions. Use standard ES2017 syntax.

Warnings

breaking Babel 7 requires 'module:fast-async' plugin prefix instead of 'fast-async' ↓

fix Use 'module:fast-async' in plugins array for Babel 7.

breaking Options 'augmentObject', 'dontMapStackTraces', 'dontInstallRequireHook' removed in v6.3.x ↓

fix Remove these options from configuration; they are no longer supported.

deprecated Compiled code typically requires nodent runtime unless 'noRuntime' or 'spec' option is used ↓

fix Either include runtime via 'runtimePattern' or set 'compiler.promises: false' if your environment supports Promises.

gotcha ES7 extensions like 'await' outside async function or 'async return' are not supported because Babel parses the code ↓

fix Only use standard async/await syntax; those extensions are only available with nodent directly.

gotcha Stack trace mapping can conflict with Babel's own mapping, causing confusion ↓

fix Ensure 'dontMapStackTraces' defaults to true; avoid enabling both mappings simultaneously.

Install

npm install fast-async

yarn add fast-async

pnpm add fast-async

Imports

default
wrong
```
import fastAsync from 'fast-async'
```
correct
```
module.exports = require('fast-async')
```
CommonJS only; no default ES import provided. Use require or dynamic import.

Quickstart

Shows basic babel plugin configuration and the transformation from async/await to Promises.

// .babelrc
{
  "plugins": ["fast-async"]
}

// Input
async function fetchData(url) {
  const response = await fetch(url);
  return response.json();
}

// Output (simplified)
function fetchData(url) {
  return Promise.resolve().then(function() {
    return fetch(url);
  }).then(function(response) {
    return response.json();
  });
}