I have an async function with multiple mysql queries like this:
const memberdata = async function() {
somequery1 = await doquery('id','table1','member_id',userid);
somequery2 = await doquery('id','table2','member_id',userid);
somequery3 = await doquery('id','table3','member_id',userid);
problem = await doquery('id','sessions','member_id',userid);
const array = {somequery1 : somequery1[0].id, somequery2 : somequery2[0].id, somequery3 : somequery3[0].id, problem : problem[0].id};
return (array);
};
memberdata().then(v => {
username = v.somequery1;
sex = v.somequery2;
age = v.somequery3;
session = v.problem
});
Most of the queries are expected to return a value because there is always at least one record on their tables. The only exception is problem where 50% of the time no record will be found thus upon declaring session I will get an error saying UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch().
That wouldnt be a problem if that was the only query but thats not the case so what can I do to have problem simply return 0 or null in case no record is found?
Thank you.
If the doquery always returns a Promise that resolves to an array, you need to check that the array is populated before accessing properties of the [0]th element.
When returning, change
problem : problem[0].id};
to
problem : problem.length ? problem[0].id : 0};
You also might consider using Promise.all to make the code run in parallel.
I think you just need to learn how if statements work.
My guess is that doQuery returns 0 or more records, and your code misbehaves if it's 0, because you are referring to:
problem[0].id
If the array has 0 elements, this triggers your error.
So the solution is to add an if statement that handles this case:
if (problem.length === 0) {
// Do something
} else {
// Do the normal thing
}