Node: Bubbling up error response with nested async/await try/catch

Question

I'm having trouble figuring out how to properly send an Express route handler response from an error generated and caught within nested try/catch blocks.

In the code below, I would like all execution of the route handler to cease if the inner Try/Catch 3 block catches an error, which will return a status 404 error. At this time, when an error is caught in Try/Catch 3, the route handler continues to execute subsequent code in Code Block A, catching and return a status 400 error in Try/Catch 1. The route hanlder then sends this 400 status response. How can I have the route handler return the Try/Catch Block 3 404 response and, therefore, never execute the code in Code Block A?

I've tried modifying return statements in various places, but can't seem to get the route handler to solely return an error caught within the inner Try/Catch 3. Can anybody see, with relative ease, where it is that I'm failing to properly return or manage the propagation of errors?

app.get("/endpoint/url", async(req, res) => {
    // Try/Catch 1
    try {

        // Define an async function
        const queryApiFunc = async() => {
            // Try/Catch 3
            try {
                let results = await axios({
                    // Axios Query to API
                })
                if (/*condition is met*/) 
                    throw "No results found";

                }
            catch (e) {
                if (e === "No results found") {
                    res.statusMessage = e;
                    return res.status(404).end();;
                }
            }
        }

        // Try/Catch 2
        try {
            // Call the defined async function
            await queryApiFunc();
        } catch (e) {
            return e;
        }

        // Code Block A 
        // contains another async call to API 
        // generates 400 status error
        // Code Block A

    } catch (e) {
        return e;
    }
}

CodyKnapp · Accepted Answer · 2018-09-07 19:24:36Z

2

It appears as though that's happening because you aren't actually throwing anything from the function. I'm not entirely sure of exactly what you're trying to accomplish, but what about a structure more like the following ?

app.get("/endpoint/url", async(req, res) => {
    const queryApiFunc = async() => {
        let results = await axios({

        });
        if (/*condition is met*/) throw "No results found";
    };

    try {
        await queryApiFunc();
        //Code Block A
    } catch (e) {
        if (e === "No results found") {
            res.statusMessage = e;
            return res.status(404).end();;
        }
    }
});

That should get rid of some of the try/catch trapping where you risk swallowing errors and then get you to the actual desired result.

edited Sep 7, 2018 at 19:24

answered Apr 21, 2018 at 16:32

CodyKnapp

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