identity

This function takes one parameter and just returns it. Simply put, this is like <T>(x: T): T => x.

Examples

This is useful in some cases when using things like mergeMap

import { interval, take, map, range, mergeMap, identity } from 'rxjs';

const source$ = interval(1000).pipe(take(5));

const result$ = source$.pipe(
  map(i => range(i)),
  mergeMap(identity) // same as mergeMap(x => x)
);

result$.subscribe({
  next: console.log
});

Or when you want to selectively apply an operator

import { interval, take, identity } from 'rxjs';

const shouldLimit = () => Math.random() < 0.5;

const source$ = interval(1000);

const result$ = source$.pipe(shouldLimit() ? take(5) : identity);

result$.subscribe({
  next: console.log
});