Node repl with async await

Question

I would like to add support to async/await to node repl

Following this issue: https://github.com/nodejs/node/issues/8382

I've tried to use this one https://github.com/paulserraino/babel-repl but it is missing async await suppport

I would like to use this snippet

const awaitMatcher = /^(?:\s*(?:(?:let|var|const)\s)?\s*([^=]+)=\s*|^\s*)(await\s[\s\S]*)/;
const asyncWrapper = (code, binder) => {
  let assign = binder ? `root.${binder} = ` : '';
  return `(function(){ async function _wrap() { return ${assign}${code} } return _wrap();})()`;
};

// match & transform
const match = input.match(awaitMatcher);
if(match) {
  input = `${asyncWrapper(match[2], match[1])}`;
}

How can I add this snippet to a custom eval on node repl?

Example in node repl:

> const user = await User.findOne();

Answer 1

The idea is to preprocess the command and wrap it in a async function if there is an await syntax outside async function

this https://gist.github.com/princejwesley/a66d514d86ea174270210561c44b71ba is the final solution

Answer 2

As of node ^10, you can use the following flag when starting the repl:

node --experimental-repl-await
$ await myPromise()

Answer 3

There is the project https://github.com/ef4/async-repl:

$ async-repl
async> 1 + 2
3
async> 1 + await new Promise(r => setTimeout(() => r(2), 1000))
3
async> let x = 1 + await new Promise(r => setTimeout(() => r(2), 1000))
undefined
async> x
3
async>

Another option, slightly onerous to start but with a great UI, is to use the Chrome Devtools:

$ node --inspect -r esm
Debugger listening on ws://127.0.0.1:9229/b4fb341e-da9d-4276-986a-46bb81bdd989
For help see https://nodejs.org/en/docs/inspector
> Debugger attached.

(I am using the esm package here to allow Node to parse import statements.)

Then you go to chrome://inspect in Chrome and you will be able to connect to the node instance. Chrome Devtools has top-level await, great tab-completion etc.