subscribe to multiple platform event channels at once

Question

I am following lightning/empApi example to subscribe to a Platform Event (PE) channel. I am able to successfully subscribe to one channel, but I cannot subscribe to multiple channels at once. I am using LWC and not any aura component.

Questions

1. How can I subscribe to multiple channels at once?
2. What would be the proper way to subscribe using empApi?

Example code

import { LightningElement } from 'lwc';
import {
    subscribe,
    unsubscribe,
    onError,
    setDebugFlag,
    isEmpEnabled,
} from 'lightning/empApi';

export default class EmpApiLWC extends LightningElement {
    channelName = ['/event/Test__e', '/event/AnotherPE__e'];
    isSubscribeDisabled = false;
    isUnsubscribeDisabled = !this.isSubscribeDisabled;

    subscription = {};
    // Handles subscribe button click
    handleSubscribe() {
        // Callback invoked whenever a new event message is received
        const messageCallback = function (response) {
            console.log('New message received: ', JSON.stringify(response));
            // Response contains the payload of the new message received
        };

        // Invoke subscribe method of empApi. Pass reference to messageCallback
        subscribe(this.channelName, -1, messageCallback).then((response) => {
            // Response contains the subscription information on subscribe call
            console.log(
                'Subscription request sent to: ',
                JSON.stringify(response.channel)
            );
            this.subscription = response;
            this.toggleSubscribeButton(true);
        });
    }
}

Error message

"400::The channel specified is not valid {/event/Test__e,/event/AnotherPE__e}"

What I tried, but didn't work

subscribe(JSON.stringify(this.channelName), -1, messageCallback).then((response) => {...}

Answer 1

Thanks to @PhilW as I was able to find a solution. I have to iterate through all possible channels to subscribe to and then subscribe in a loop.

for(let i = 0; i < this.channelName.length; i++) {
    subscribe(this.channelName[i], -1, messageCallback).then((response) => {...}
}