firebase function state pending and return undefined - reactjs

Question

I'm trying to make an input form that will check if the data exists in firebase database, below is the code that I used to check the data :
if(element.validation.codeunique) {
function checkCode(inputcode) {
firebaseUsers.orderByChild('code')
.equalTo(inputcode).once('value')
.then( snapshot => {
let thecode = null;
if(snapshot.val()){
thecode = false;
} else {
thecode = true;
}
console.log(thecode)
})
}
let checkcode = null;
checkcode = checkCode(element.value);
console.log(checkcode)
const valid = checkcode;
const message = `${!valid ? 'Code Exists':''}`;
error = !valid ? [valid,message] : error
}
in database i have a data :
users
-L3ZeHOI7XOmP9xhPkwX
-code:"DEM"
when I entered data DEM at the form :
console.log(thecode) result is false (which is the result that i want)
and when i entered another data ASD at the form :
console.log(thecode) result is true(which is the result that i want)
so the firebaseUsers actually is giving me the feedback/data that I want, but when I tried to get the data at valid with true/false,
this is the code that I originally used:
if(element.validation.codeunique) {
function checkCode(inputcode) {
firebaseUsers.orderByChild('code')
.equalTo(inputcode).once('value')
.then( snapshot => {
if(snapshot.val()){
return false;
} else {
return true;
}
})
}
const valid = checkCode(element.value);
const message = `${!valid ? 'Code Exists':''}`;
error = !valid ? [valid,message] : error
}
the valid shows = undefined,
my goal is to make the valid shows true/false,
could someone help me, and point out, what did i do wrong?
*I make the first code just to point out that the firebase is actually working
*the second code is the one that I originally used

Answer 1

There are a few issues that are standing out to me.
First, the code that you use originally was using return inside of the function's if / else conditional. I believe this is correct, you'll want to go back to doing that.
Second, the firebase.orderByChild() function that you are calling is a Promise as it has a .then() statement appended to it. What this means is that the function does not synchronously finish executing and return a value. The code below that promise is being run while the firebase function is still processing.
Give this a shot and see if it works, and if you have any further errors beyond the promise.
if(element.validation.codeunique) {
function checkCode(inputcode) {
firebaseUsers.orderByChild('code')
.equalTo(inputcode).once('value')
.then( snapshot => {
if(snapshot.val()){
return false;
} else {
return true;
}
console.log(thecode)
})
}
let message = checkCode(element.value) ? 'Code Exists':'Code Does not Exist';
}

Answer 2

I've done it outside of the function above and by checking it when the user submit the form, and if the code exists, i direct it to form again :
firebaseUsers.orderByChild('code')
.equalTo(mycode)
.once('value')
.then (snapshot => {
if(snapshot.val()) {
alert("Code Exists, Please Choose another");
this.props.history.push('/myscreen')
} else {
//submit the data
}
hopefully this will help someone