How do I make an "async/await" operator for Jint?

[MauryDev]

I made a function in C# for Promise, Async and Await, but I don't want it to be "async / await" functions in javascript, but an operator.

It works in my custom Jint.Engine like that

var async_example = async(function()
{
  return 2;
})
var t = async_example();
console.log(await(t))
// 2

But I would like it that way:

var async_example = async function()
{
  return 2;
}
var t = async_example();
console.log(await t)
// 2

I wanted to add the "async / await" operator to Jint. Please help me.

[danbopes]

Promises have yet to have been implemented. (So no async/await yet)

[lahma]

You might want to follow the building block PR, Promises.

[koculu]

I have created a partial, blocking and simple await support for C# Tasks and ValueTask.
This might be a temporary solution until real await comes in.
https://gist.github.com/koculu/86cf538bcd4411d84e6206cc7fe7758f

@sebastienros Would it be fine if you add this partial support until proper await implementation done?
This can let people to write async scripts with await instead of converting everything to Promises.

[lahma]

Closing this as duplicate of #514 , we have the promises, but async/await needs to be done. I think generators need to be done as it has some building blocks once again.

[lahma]

async/await has been implemented as first class citizen in main branch.

[sfmskywalker]

Hi @lahma , does this also mean one could set an C# function that returns a Task that can be awaited in JS? For example:

engine.SetValue("testAsync", (Func<Task<object?>>)(async () => await Task.FromResult(new { foo = "bar" })));

I tried this with the following JS:

const bar = await testAsync();

Which throws a ParserException with "Unexpected identifier".

[lahma]

Sorry I've been a bit absent as my wife passed away a month ago and I had to prioritize things a bit. I think there's a PR #1567 that tries to fill the gap between .NET Task and JS's async, but there might be dragons.

If you get Unexpected identifier that might signal that you are not in async context as that's something that is being expected by the parser at the moment (inside async function).

[sfmskywalker]

Sorry for your loss Marko. I noticed you have merged that PR, which is fantastic - thank you! I'll go take a look.

[sfmskywalker]

I never reported back, but I wanted to let you know that the bridging from Promise to Task and the async/await keywords work super amazing 😍