Function and module.exports error issue NODE.js - node.js

Question

:)
I have a somewhat easy answer for you guys to answer as you always do.
Im new at functions and whatnot, iv watched some tutorials about exporting your functions to another node.js application,
Im attempting to generate some random numbers for a external module.
this is what i have setup.
(index.js file)
function randNumb(topnumber) {
var randnumber=Math.floor(Math.random()*topnumber)
}
module.exports.randNumb();
(run.js)
var index = require("./run.js");
console.log(randnumber);
Well My Issue is when i run the index.js file, i get this error from the console.
TypeError: Object #<Object> has no method 'randNumb'
at Object.<anonymous> (C:\Users\Christopher Allen\Desktop\Node Dev Essential
s - Random Number\index.js:8:16)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.runMain (module.js:492:10)
at process.startup.processNextTick.process._tickCallback (node.js:244:9)
I ran the run.js in the beginning, this is what i got.
ReferenceError: randNumb is not defined
at Object.<anonymous> (C:\Users\Christopher Allen\Desktop\Node Dev Essential
s - Random Number\run.js:3:1)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.runMain (module.js:492:10)
at process.startup.processNextTick.process._tickCallback (node.js:244:9)

Answer 1

In the randNum function, don't forget to:
return randnumber;
Also in index.js, export the function like so:
exports.randNumb = randNumb;
Invoke it like this in run.js:
console.log(randNumber(10));

Answer 2

You didn't export the var at all.
Your index.js should be :
function randNumb(topnumber) {
return Math.floor(Math.random()*topnumber)
}
module.exports.randnumber = randNumb(10); //replace 10 with any other number...
run.js should be :
var index = require("./run.js");
console.log(index.randnumber);