RxJS concat() Join Operator

The RxJS concat() operator is a join operator that creates an output Observable, which sequentially emits all values from the given Observable and then proceed to the next one.

Syntax:

Following is the syntax of the concat() operator:

Parameter Explanation

observables: It specifies that the input given is an array of Observables.

Return value

The concat() operator's return value is an observable that gives a single value merged from the values of the different source observables.

Let us see an example of concat() operator to understand it clearly.

Example

import { of } from 'rxjs';
import { concat } from 'rxjs/operators';
let list1 = of(2, 4, 6, 8, 10, 12, 14, 16, 18, 20);
let list2 = of(1, 3, 5, 7, 9, 11, 13, 15, 17, 19);
let final_val = list1.pipe(concat(list2));
final_val.subscribe(x => console.log(x));

Output:

After executing the above example, you will see the following result: