Question

111

Determining string length in Node JS when string may be null

rated 0 times [ 117] [ 6] / answers: 1 / hits: 45870 / 12 Years ago, thu, may 17, 2012, 12:00:00

I'm trying to learn Node and have the function:

this.logMeIn = function(username,stream) {

  if (username === null || username.length() < 1) {

    stream.write(Invalid username, please try again:nr);

    return false;

  } else {

  ....etc

and I'm passing it

if (!client.loggedIn) {

  if (client.logMeIn(String(data.match(/S+/)),stream)) {

I've tried both == and ===, but I'm still getting errors as the username is not detecting that it is null, and username.length() fails on:

if (username === null || username.length() < 1) {

                                  ^

TypeError: Property 'length' of object null is not a function

I'm sure that Node won't evaluate the second part of the || in the if statement when the first part is true - but I fail to understand why the first part of the if statement is evaluating to false when username is a null object. Can someone help me understand what I've done wrong?

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terrellhunterm

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4 Years ago

answered 12 Years ago reecep · Accepted Answer

You're passing String(data.match(/S+/)) as username argument, so when data.match(/S+/) is null, you get null not null for username, as:

String(null) === null

So you need to change your condition:

if( username === null || username === null || username.length < 1 )