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identity.ts
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identity.ts
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/**
* 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`
*
* ```ts
* 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
*
* ```ts
* 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
* });
* ```
*
* @param x Any value that is returned by this function
* @returns The value passed as the first parameter to this function
*/
export function identity<T>(x: T): T {
return x;
}