Cannot assign value to variable by reference in Javascript

Question

I would like to assign value to the variable IMLoginReq inside a ProtoBuf load function, but its not working, can anyone help?

var IMLoginReq;
protobuf.load("./pb/IM.Login.proto", (err, root) => {
    // Obtain a message type
    IMLoginReq = root.lookup("IM.Login.IMLoginReq");
    console.log(IMLoginReq);//<== is not undefined
});
console.log(IMLoginReq);//<== is undefined

I am using dcodeIO.protobuf to fetch my request definition proto, so the request is originally defined by myself — Ethan Programmer, Dec 20 '16 at 04:27

score 1 · Accepted Answer · answered Dec 20 '16 at 02:56

1

The load() method is asynchronous. As such the console.log at the end will happen before the load finishes. Instead of trying to treat this as procedural logic, which it is not, you should instead use the IMLoginReq inside the success method that you have.

answered Dec 20 '16 at 02:56

Taplar

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This of course assumes that the load() is the jQuery method, though by your issue even if it is not, the load() is still appearing to be asynchronous. – Taplar Dec 20 '16 at 02:57
This is the answer how it happened like that, very appreciate. – Ethan Programmer Dec 20 '16 at 04:28

score 0 · Answer 2 · answered Dec 20 '16 at 02:57

0

Thats because you are trying to call it before its loaded. You should have a callback function like success so it will be there. You can also use promises by omitting the callback:

protobuf.load("awesome.proto")
    .then(function(root) {
       ...
    });

answered Dec 20 '16 at 02:57

flakerimi

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Thanks for your inspiration – Ethan Programmer Dec 20 '16 at 04:28

Cannot assign value to variable by reference in Javascript

2 Answers2