CODEWITHSUNDEEP
javascriptnode.jsexpress
AndoKay
AndoKay

Reputation: 57

Conditionally Sending Response in Catch Block

I'm trying to figure out the proper way to handle a potential bad Fetch response. If the Fetch response is not okay, I want to immediately send a 500 response and and stop the rest of the code from executing. But if the response is okay, I want to continue the program and send a response at the end. My code does seem to work properly at the moment but I get

UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client.

I assume this is because program continues after the catch block and tries to send the second response. Again, the code works but this is obviously not the right way to do it. Is there way I can get the program to stop executing after the response in the catch block is sent?

app.get('/route', async function(req, res){
   
    try{
        let response = await fetch('https://www.google.com/NonExistantPage')
        if(!response.ok)    
            throw new Error("err")
    }catch{
        res.status(500).end()
    }
    /*
    Program continues if fetch was successful
    */
    res.send("data")
    
})

Upvotes: 0

Views: 1787

Answers (2)

farzam
farzam

Reputation: 33

try-catch is async so don't need to set async function. I use this:

app.get('/route',(req, res)=>{        
    try 
    {
        let response = await fetch('https://www.google.com/NonExistantPage')

        if(!response.ok) {
            throw new Error("err")
        }
    }
    catch (err) 
    {
        /* handle errors */
    } 
    finally
    {
        res.status("status code")
        
        // send data and other things ...
        res.send("data")
        return.end()
    }
})

Upvotes: 0

Dinesh Nadimpalli
Dinesh Nadimpalli

Reputation: 1491

Your code is trying to call the res.send("data") even though it sets the response when error occurs inside catch res.status(500).end(). Try returning the response to break the execution of the final response once the response headers are set inside catch as shown below

app.get('/route', async function(req, res){
   
    try{
        let response = await fetch('https://www.google.com/NonExistantPage')
        if(!response.ok)    
            throw new Error("err")
    }catch{
        return res.status(500).end()
    }
    /*
    Program continues if fetch was successful
    */
    return res.send("data")
    
})

Upvotes: 2

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