A brief look at async-await

  check()
    .then(result => {
      if (result) {
         // set state to finished
      }
      check()
        .then(result => {
          if (result) {
              // set state to finished
          }
          check()
            .then(result => {
              if (result) {
                 // set state to finished
              }
              check()
                .then(result => {
                  if (result) {
                    // set state to finished
                  }
                  check()
                    .then(result => {
                      if (result) {
                         // set state to finished
                      }

                      // set state to not done
                    })
                    .catch(error =>  // set state to failed);
                })
                .catch(error =>  // set state to failed);
            })
            .catch(error =>  // set state to failed);
        })
        .catch(error =>  // set state to failed);
    })
    .catch(error =>  // set state to failed);

  const resultOrNull = await Promise.resolve(null).
       then(result => result || check()).
       then(result => result || check()).
       then(result => result || check()).
       then(result => result || check()).
       then(result => result || check()).
       catch(error => null);

CPS in scheme works because proper tail call optimization exists, so your call stack doesn't explode. In current JS, the only way to make that work is performing a nextTick or setTimeout on every single function which trashes performance of simple things due to exiting your code back to the event loop all the time.

There's a special place in hell reserved for companies that deviate from standards because of petty disagreements. Proper tail calls have been a part of the JS spec for 5 versions now. They are implemented in Safari and in popular embedded engines like duktape. MS and Firefox refused to implement. They were in v8 behind a flag, but were removed.

v8 devs pitched a fit about stack traces disappearing (even though they disappear across the event loop anyway). The webkit team showed that Chicken scheme's shadow stack works just fine and it's been in production for a long time now (without any issues I'd add). Instead, they insisted that they wanted to revise the standard to require marking tail-recursive functions.

They also talked about decreased performance, but JSC team seems to have implemented it with a minimal performance impact, so it's definitely possible. More importantly, JS is a language to make development easy -- we have wasm in development for when speed becomes an issue and it's faster anyway (the label proposal would have also solved the issue by giving devs a choice).

They then dropped their own proposal, but still simply refused to re-add the feature as per the spec in a bid to force a spec change. I have some understanding of not turning a feature on until a newer proposal is considered, but when they dropped that proposal and still refused to implement, they lost all credibility in my estimation.

https://webkit.org/blog/6240/ecmascript-6-proper-tail-calls-...

https://www.more-magic.net/posts/internals-gc.html

I think this is indicative of a general "we know better than you" attitude on the part of the engine designers (especially the ones that sit on the spec committee). Another amazing example of this is the private variable proposal. NEVER has a JS proposal received such outspoken disapproval. Complaints range from the mostly insignificant "it's ugly" to the important "it goes against JS's core prototypical nature" to the very important "refactoring and maintaining this will be a nightmare due to dedicated syntax and JS being so dynamic", "it looks like a normal JS property that is hidden, but it in fact has almost nothing in common with normal properties even though the access syntax looks similar" or "this screws with inheritance, subclassing, destructuring syntax, etc".

Instead of listening, they locked down all dissenting discussions on the proposal's github and are going full steam ahead. EDIT: some discussions are unlocked (see below for a decent argument summary).

https://github.com/tc39/proposal-class-fields/issues/150

Decorators, pipe operators, tuples, immutable records, and slice notation are all well-understood ideas. Most don't require huge amounts of work to implement, but result in large quality-of-life improvements for developers. Most importantly, they aren't really controversial at all and most are easily transpilable so devs could start using them today (unlike private vars which either don't actually transpile correctly or create a mountain of unreadable garbage)

Why can't we work on these things that have such wide user impact instead of forcing through controversial changes that only benefit a very few people?

    function check() {
        return new Promise(async (resolve, reject) => {
            for(let i = 0; i 

    async function check() {
        for(let i = 0; i