Node.js Modifying variable from different file

Question

I'm new in Node.js and I wondering something. I'm use express and socket.io. there is some value to should be changeable, let's say this 'flag' that have boolean type variable - this is 'false' at default.

but some moment especially when I click some button, it would be change to 'true'. the express and socket.io workflow is fine, but I don't know how to modifying variable from different file not just copying it.

Please see below code to understand

Main.js

var flag = false;
exports.flag = flag; 

// display flag every second
setInterval((function(){console.log(flag)}), 1000);

Remote.js

// I want to change 'original flag' at main.js in remote.js 
// How can I do that? I think below is just copying it, so doesn't effect to main.js

flag = require('/Main').flag;

// the flag will be 'true' after some moment
flag = true;

expected result I want in main.js

false
false
false
...
true
true

How can I do that?

RPDeshaies · Accepted Answer · 2016-01-08 18:33:20Z

2

Have you tried using the included object instead of the property ?

That way you keep a reference on the object and not the primitive value.

main = require('/Main');

main.flag = true;

Edit : As said in the comment by Mike C, you would also need to use the object in the setInterval

setInterval((function(){console.log(exports.flag)}), 1000);

It works because Object is a reference type, compared to string or boolean which are primitive.

edited Jan 8, 2016 at 18:33

answered Jan 8, 2016 at 18:17

RPDeshaies

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2 Comments

Mike Cluck Over a year ago

They'd also have to change the code in main.js to use exports.flag in the setInterval.

RPDeshaies Over a year ago

Added more details :)

Naeem Shaikh · Accepted Answer · 2016-01-08 18:21:36Z

1

you can define a global variable and access is or change it wherever you want.

main.js

global.flag = false; 

// display flag every second
setInterval((function(){console.log(global.flag)}), 1000);

remote.js

// the flag will be 'true' after some moment
global.flag = true;

answered Jan 8, 2016 at 18:21

Naeem Shaikh

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1 Comment

ton1 Over a year ago

Thank you too, maybe this is easy way.

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