I am very confused about which if these three is correct.
A(){
Return promise
}
Async A(){
Return promise
}
Async A(){
Return await promise //this seems very wrong but still...
}
Which of these are correct JavaScript? And if more than one is correct, what is the best practice here, if any?
Async/await can be considered as syntax sugar for Promises. Any function that returns a Promise object can be used as an async function. The two styles (promise style vs. async/await style) can be mixed without issue.
function A() {
return Promise.resolve('foo');
}
async function B() {
var aResult = await A();
return aResult;
}
B().then(console.log);
Best practice would be to pick one style and stick with it, for readability. Async/await is the newer style, and has the advantage that it avoids the .then pyramid of doom.
Note that async/await, or even promises, may not be supported in all runtimes and may require a transpiler (like babel).
You could use all of them as all three are valid. But given your examples, only the first makes sense.
Each of your examples returns a Promise. You can either use a().then(/*...*/) or await a() (only within an async function) to get their response when they resolve. Read more about Promise or async/await in general.
function a() {
return Promise.resolve();
}
This is how you should write a function that returns a Promise.
async function a() {
return Promise.resolve();
}
This works as well, but only functions that actually use the await keyword need to be annotated with async. Functions that just return a Promise without using await in their body do not need to be async.
Async A(){ Return await promise //this seems very wrong but still... }
