Turn your JavaScript with async functions into ES6 generators so they can be used in modern browsers or in node.js (v0.12 or newer).
Async functions are an exciting new proposed addition to JavaScript. The v8 team is hard at work getting it right, which means it could appear in future versions of node.js. However if you're impatient like me, then you probably just can't wait to get rid of your promise triangles and callback hell.
You can use Babel to accomplish this, but async-to-gen
is a faster, simpler, zero-configuration alternative with minimal dependencies
for super-fast npm install
and transform time.
Use the command line:
npm install --global async-to-gen
async-to-gen --help
async-to-gen input.js > output.js
Or the JavaScript API:
npm install async-to-gen
var asyncToGen = require('async-to-gen');
var fs = require('fs');
var input = fs.readFileSync('input.js', 'utf8');
var output = asyncToGen(input);
fs.writeFileSync('output.js', output);
Wherever you use node
you can substitute async-node
and have a super fast
async functions aware evaluator or REPL.
$ async-node
> async function answer() {
... return await 42
... }
undefined
> promise = answer()
Promise { <pending> }
> promise.then(console.log)
Promise { <pending> }
42
Using the require hook allows you to automatically compile files on the fly when requiring in node:
require('async-to-gen/register')
require('./some-module-with-async-functions')
Writing tests in mocha? Async functions are super handy for testing any code using promises and already work out of the box! To enable async functions in mocha include the require hook when you run your tests:
mocha --require async-to-gen/register test.js
Then in your tests, use async functions in your it
clauses:
describe('My Promising Module', () => {
it('promises to give a value', async () => {
expect(await myFunction('input')).to.equal('output')
})
})
Have interactive scripts that require lots of input from the user? Async functions make writing those much easier! Check out interactive-script.
npm install interactive-script
Then write your script:
const interactive = require('interactive-script')
interactive(async (say, ask) => {
say('What is your favorite number?')
let num;
do {
num = Math.ceil(Math.random() * 100)
} while (!(await ask(`Is it ${num}? `, 'yN')))
say(`Great, I think ${num} is a fine number.`)
})
And run it with async-node
:
async-node myScript.js
When async-to-gen
transforms async functions, it does not affect the location
of lines in a file, leading to easier to understand stack traces when debugging.
It also includes a very small (236 byte) conversion function at the bottom of the file.
Before:
async function foo() {
return await x
}
After:
function foo() {return __async(function*(){
return yield x
})}
function __async(f){/* small helper function */}