JavaScript using async/await from a class

Question

I have a JavaScript class and I am trying to figure out how to use the new async/await keywords in the connect method.

module.exports = class {
    constructor(url) {
        if(_.isEmpty(url)) {
            throw `'url' must be set`;
        }

        this.url = url;
        this.client = new MongoClient(url, {
            useNewUrlParser: true
        });
    }

    connect() {
        this.client.connect(async (error) => {
            if(error) {
                throw error;
            }
        });
    }
};

Essentially I want wait until connect() returns from the callback. I added async in front of the callback, but don't I need an await statement as well? I am getting a UnhandledPromiseRejectionWarning from Node.js.

Alex Broadwin · Accepted Answer · 2019-02-11 20:58:12Z

2

If connect is an async function/returns a promise then you can await the call if you're calling it from within an async function, like so:

async connect() {
        await this.client.connect(async (error) => {
            if(error) {
                throw error;
            }
        });
    }

answered Feb 11, 2019 at 20:58

Alex Broadwin

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2 Comments

Darlesson Over a year ago

He may not need async in front of (error) => { anymore.

Alex Broadwin Over a year ago

True, and depending on how connect is written it may not even need the error callback at all as it may already be rejected and then thrown by the awaited statement.

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