Add delay to javascript method that returns promise
Delayed native promise
New promise that resolves with undefined
return new Promise(resolve =>
setTimeout(resolve, 5000)
);
New promise that resolves with a value
return new Promise(resolve =>
setTimeout(() => resolve(value), 5000)
);
Existing promise
return promise.then(value =>
new Promise(resolve =>
setTimeout(() => resolve(value), 5000)
)
);
Delayed Bluebird promise
Bluebird promise library has better performance and convenient features that can be used out of the box to delay promise chains.
New promise that resolves with undefined
return Bluebird.delay(5000);
New promise that resolves with a value
return Bluebird.resolve(value).delay(5000);
// or
return Bluebird.delay(5000).return(value);
Existing promise
return bluebirdPromise.delay(5000);
Delayed promise with RxJS
RxJS is already used in Angular 2/4 projects and can be used to create or transform promises with RxJS operators and small overhead.
New promise that resolves with undefined
return Observable.of().delay(5000).toPromise();
// or
return Observable.interval(5000).first().toPromise();
New promise that resolves with a value
return Observable.of(value).delay(5000).toPromise();
Existing promise
return Observable.fromPromise(promise).delay(5000).toPromise();
Delayed result with RxJS 6
You can use the following code to delay values in RxJs 6 by n
ms.
With no specific value (will emit 0
)
return timer(n);
With a set value
return of(value).pipe(delay(n));
or
return timer(n).pipe(mapTo(value));
from a promise
return from(promise).pipe(delay(n));
to return a promise
put .toPromise()
on any of the previous examples after the pipe
.
return timer(n).toPromise();
return of(value).pipe(delay(n)).toPromise();
etc.