CODEWITHSUNDEEP
javascriptnode.jspromise
Catalyst
Catalyst

Reputation: 338

Return a bool or string inside a Callback in NodeJS

I am writing Unit Testing which require me to hit the exceptions. Incase of promises, I cannot really send any boolean or string values. My intended output and the one I am getting is mentioned below.

function mainFunction(registry, name,....){
    justAnotherPromiseFunction(name, function (err, twin) {
        if (err) {          
            return "I want to return a failure message here!";
        } else {
            <MyLogic Goes Here>
        }
    });
}
console.log(mainFunction(registry, name,....));

This returns Promise { <rejected> [ArgumentError: The connection string is missing the property: Something] }.

Instead of I want to return a failure message here!.

Any ideas on how I can manage to do this?

Edit: I am implementing a function from azure sdk that uses promises. So looks like this:

function mainFunction(){
    registry.getTwin(name, function (err, twin) {
        if (err) {          
            return "I want to return a failure message here!";
        } else {
            <My Business Logic Goes Here>
        }
    });
}
console.log(mainFunction());

Upvotes: 1

Views: 159

Answers (1)

Eduard Hasanaj
Eduard Hasanaj

Reputation: 895

You are using it in the wrong way. You cannot print the result of promise just by callint it. A promise return its result in the then function. Please see following examples.

async function mainFunction() {
    try {
        const result = await myPromise();
        return result;
    }
    catch (err) {
        return 'I want to return a failure message here!'
    }
}

function myPromise() {
    return new Promise(function(resolve, reject) {

    })
}

it("test async function", async() => {
    console.log(await mainFunction())
})

Make your test function async so you can await for the result.

Upvotes: 2

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