Blade does not accept variable - laravel-5

Question

This is my code
var feetype="{{App\StudentFee::where('id', '2')->value('student_fee_type')}}";
console.log(feetype);
Works perfectly fine.
However when I try to modify it like so
var fee_type_id = 2;
var feetype="{{App\StudentFee::where('id', fee_type_id)->value('student_fee_type')}}";
console.log(feetype);
It throws the following error
Use of undefined constant fee_type_id - assumed 'fee_type_id' (this will throw an Error in a future version of PHP)
What am I doing wrong?

Answer 1

PHP is run server side.
After it is done the content it generated is download to the client side where you work with javascript
Therefore your javascript variables wont be accessible to PHP on the server.
There are workarounds to give PHP the variables to work with.
Here you can find an example of this https://laravel.com/docs/5.8/routing#required-parameters.
You can for example append this to your route /{fee_type_id} and pass the variable at the end of requested url. In you can than add in your code
var feetype="{{App\StudentFee::where('id', $fee_type_id)->value('student_fee_type')}}";
Provided you pass the variable to wherever you need it.
I hope this works for you.

Answer 2

You have not escaped the phrase fee_type_id in quotes so it is used as a constant however that constant is undefined. You probably meant to pass in a variable $fee_type_id.
Really though, you should be passing what you need into the blade view instead of performing eloquent model db queries inside the view.