node.js callback sample

callbackwitherr.js

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

division(5,4,function(err,result) {
    if(err==null) {
		console.log(result);
	}
});