将while循环中的异步等待转换为promise

Question

I can't figure out how to convert async await functionality in a while loop to a promise based implementation.

repl showing the async await version

https://repl.it/repls/IdealisticPepperyCoding

 var dependency = false; function checkDependency() { return new Promise(resolve => { setTimeout(() => { dependency = true; return resolve(); }, 1000) }); } async function isReady() { while(!dependency) { console.log('not loaded'); await checkDependency(); } console.log('loaded') } isReady(); 

Answer 1

If I'm understanding you correctly, you're wanting to use Promises without async functions instead of Promises with async functions, and the sample checkDependency may actually not set dependency = true in all cases, so you want to "loop."

Equivalent functionality could look something like this, where you "recursively" call the check function. It won't actually be recursive and lead to a stack overflow, though, since the call is done in an async callback:

var dependency = false;

function checkDependency() {
  return new Promise(resolve => {
    setTimeout(() => {
      dependency = true;
      return resolve();
    }, 1000)
  });
}

function isReady() {
  if (!dependency) {
    return checkDependency().then(isReady);
  }

  return Promise.resolve(true);
}

isReady().then(() => {
  console.log('loaded')
});

Answer 2

您不需要while循环。

 checkDependency().then(() => { console.log('loaded');}); 

Answer 3

• You don't need to return recolve() just call it.
• Call the function then within the function isReady

 function checkDependency() { return new Promise(resolve => { setTimeout(resolve, 1000); }); } function isReady() { console.log('not loaded'); checkDependency().then(() => { console.log('loaded') }); } isReady();