99. Write a function to implement a simple pub/sub pattern.

Example:

class PubSub {
    constructor() {
        this.events = {};
    }

    subscribe(event, callback) {
        if (!this.events[event]) {
            this.events[event] = [];
        }
        this.events[event].push(callback);
    }

    publish(event, data) {
        if (this.events[event]) {
            this.events[event].forEach(callback => {
                callback(data);
            });
        }
    }
}

const pubsub = new PubSub();

pubsub.subscribe("message", data => {
    console.log(data);
});

pubsub.publish("message", "Hello World");

Output:
Hello World

100. Write a function to implement a basic Promise.all.

Example:

function promiseAll(promises) {
    return new Promise((resolve, reject) => {
        let results = [];
        let completed = 0;

        promises.forEach((promise, index) => {
            Promise.resolve(promise)
                .then(result => {
                    results[index] = result;
                    completed++;

                    if (completed === promises.length) {
                        resolve(results);
                    }
                })
                .catch(reject);
        });
    });
}


promiseAll([
    Promise.resolve(1),
    Promise.resolve(2),
    Promise.resolve(3)
])
.then(console.log);

Output:
[1, 2, 3]

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