I have created a post request that receives a users ethereum address from the users end. Next I need to add the string to the users existing record in a mongoDB database.

app.post('/post', async (req,res) => {
    res.set({ 'Content-Length': 64 })
    res.json(req.body)
    const address = JSON.stringify(req.body.address)
    let temp = address.length-2;
    var walletAddress = address.slice(2, temp) //This is to remove brackets and speech marks from the string
    walletAddress = utils.getAddress(walletAddress)
    console.log(walletAddress);
    res.end("yes");
    //saving data in an existing mongodb
    
});

I've tried so many different ways and they have all presented an error off some kind.

Sorry if this is really obvious I am a noob, but help is greatly appreciated