Correct Try…Catch Syntax Using Async/Await

Question

I like the flatness of the new Async/Await feature available in Typescript, etc. However, I\'m not sure I like the fact that I have to declare the variable I\'m

Answer 1

I usually use the Promise's catch() function to return an object with an error property on failure.

For example, in your case i'd do:

const createdUser = await this.User.create(userInfo)
          .catch(error => { error }); // <--- the added catch

if (Object(createdUser).error) {
    console.error(error)
}

If you don't like to keep adding the catch() calls, you can add a helper function to the Function's prototype:

Function.prototype.withCatcher = function withCatcher() {
    const result = this.apply(this, arguments);
    if (!Object(result).catch) {
        throw `${this.name}() must return a Promise when using withCatcher()`;
    }
    return result.catch(error => ({ error }));
};

And now you'll be able to do:

const createdUser = await this.User.create.withCatcher(userInfo);
if (Object(createdUser).error) {
    console.error(createdUser.error);
}

---

EDIT 03/2020

You can also add a default "catch to an error object" function to the Promise object like so:

Promise.prototype.catchToObj = function catchToObj() {
    return this.catch(error => ({ error }));
};

And then use it as follows:

const createdUser = await this.User.create(userInfo).catchToObj();
if (createdUser && createdUser.error) {
    console.error(createdUser.error);
}