sample module in node.js

div.js

exports.division=function(num1,num2,callback) {
    if(num2 <=0 ) {
        callback("num2 shouldn't be less than or equal zero");
    }
    callback (null,num1/num2);
}

sample.js

var div = require("./div.js");

div.division(8,2,function(err,result){
	if(err==null) {
		console.log(result);
	}
});