timestamp

Attaches a timestamp to each item emitted by an observable indicating when it was emitted

timestamp<T>(timestampProvider: TimestampProvider = dateTimestampProvider): OperatorFunction<T, Timestamp<T>>

Parameters

Returns

OperatorFunction<T, Timestamp<T>>: A function that returns an Observable that attaches a timestamp to each item emitted by the source Observable indicating when it was emitted.

Description

The timestamp operator maps the source observable stream to an object of type {value: T, timestamp: R}. The properties are generically typed. The value property contains the value and type of the source observable. The timestamp is generated by the schedulers now function. By default it uses the async scheduler which simply returns Date.now() (milliseconds since 1970/01/01 00:00:00:000) and therefore is of type number.

Example

In this example there is a timestamp attached to the documents click event.

import { fromEvent } from 'rxjs';
import { timestamp } from 'rxjs/operators';

const clickWithTimestamp = fromEvent(document, 'click').pipe(
  timestamp()
);

// Emits data of type {value: MouseEvent, timestamp: number}
clickWithTimestamp.subscribe(data => {
  console.log(data);
});