how to use the concat function from the rxjs library in typescript

The concat operator concatenates multiple observables together, one after the other, emitting values in the order they are provided. Here's an example of how to use the concat function from the rxjs library in Typescript:

index.ts
import { concat, of } from 'rxjs';

const observable1 = of('hello');
const observable2 = of('world!');

const concatenated = concat(observable1, observable2);

concatenated.subscribe((val) => console.log(val));
// Output: 'hello', 'world!'
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In this example, we create two observables (observable1 and observable2) that emit a single string value each. Then, we use the concat operator to combine them into a new observable called concatenated. This new observable will emit the values from observable1 first, and then emit the values from observable2. Finally, we subscribe to the concatenated observable and log each emitted value to the console. The output of this code will be 'hello', then 'world!'.

Note that we import both the concat operator and the of operator from the rxjs library. The of operator is used to create the observables that we are concatenating together.