NaN Node.Js Callback Issue

Question

NaN Node.Js Callback Issue

I've been fumbling around with this issue for what has seemed like weeks, and I cannot get the issue resolved.

I spent days trying to get to where I can be able to call the actual function outside of the original .js file.

All I want to be able to do in node.js is create a function that will be able to generate a random number within a specific parameters such as (1-10 or 1-100), and relay it back to the console or a variable specified by the user.

This is the current code that I have:

server.js

var myModule = require("./my_module.js");
console.log("your random number is" + myModule.hello(10));  //<-- the 10 represents the TOP number that will generate, if you look in the proceeding file, it adds a 1 to it as required by the code

my_module.js

function hello(foo) {
return Math.floor((Math.random()*foo)+1);
}

module.exports.hello = hello;

The issue that underlines here is i get a NaN, ( not a number ) from the console. I realize that this means somewhere in translation, the number may be turning into a string and not being able to be read by the mathFloor string.

string
node.js
variables
math

Answer 1

You can use the jQuery method isNumeric to validate whether they gave you a number. http://api.jquery.com/jQuery.isNumeric/

To make sure it is still a number and you didn't inadvertently make it a string, use parseInt() or parseFloat().

function hello(foo) {
return Math.floor((Math.random()*parseInt(foo))+1);
}

Answer 2

While Erik's answer solves the problem, it won't tell you where the string is coming from. You can use console.trace to make your debugging life easier.

function hello(foo) {
   var result = Math.floor((Math.random()*parseInt(foo))+1);
   if (isNaN(result)) {
      console.trace("result is NaN")
   }
   return result;
}

> hello("a")
Trace: NaN
    at hello (repl:4:9)
    at repl:1:2
    at REPLServer.self.eval (repl.js:109:21)
    at Interface.<anonymous> (repl.js:248:12)
    at Interface.EventEmitter.emit (events.js:96:17)
    at Interface._onLine (readline.js:200:10)
    at Interface._line (readline.js:518:8)
    at Interface._ttyWrite (readline.js:736:14)
    at ReadStream.onkeypress (readline.js:97:10)
    at ReadStream.EventEmitter.emit (events.js:126:20)
    at emitKey (readline.js:1058:12)
    at ReadStream.onData (readline.js:807:7)
NaN
>

By looking at the stack trace you will be able to find the code that provided a non-Number parameter.