node.js - mongoose findOne returns undefined

Question

I have a method "GenerateTokenString()" that generates a random key after creating the key i passed it to a function IsTokenExists but this function returns undefines although their is a key exists in the database.

key = GenerateTokenString();

            //Check if key already exists
            var isExists=IsTokenExists(key) //undefined

function IsTokenExists(key){
     Token.findOne({token:key}).then(doc=>{
         console.log(doc)
         return doc
     }).catch(err=>{
         console.log(err)
         return err
     })
    }

Answer 1

You're trying to return a value from then to the function IsTokenExists but you don't use it to return it from IsTokenExists:

//Check if key already exists
try {
  var isExists = await IsTokenExists(key) //undefined
} catch (err) {
  console.error(err);
}

async function IsTokenExists(key){
  return Token.findOne({token:key})
}