How to create an if statement that checks the values variables are all non-null?

Question

I am currently new to javascript and running through some of my textbooks coding projects and the current problem asks to create an if statement that checks the values of the elements referenced by the name fname, lname, and zip are all non-null.

This is the code I have so far for the script

var newAccountArray = [];

function createID() {
var fname = fnameinput;
var lname = lnameinput;
var zip = zipinput;
var account = accountidbox
var fields = input;
var acctid;
var firstInit;
var lastInit;

if ( !== null)



}

I was wondering if I had to do something different for multiple variables

use if (myVar) or if (myVar !== null)

The Textbook is referring to the elements of fname, lname, and zip. Which are fnameinput, lnameinput, and zipinput — Kab, Oct 14 '17 at 17:40
Find a common point of entry... for e.g. where these variables are created ..or may be add them into an array...& then check in a loop if current element is null or not... Show the full code — Rohit Kumar, Oct 14 '17 at 17:44
I wanted to ask how do I write it so it checks three variables for null instead of just one? — Kab, Oct 14 '17 at 17:44
@RohitasBehera You left out `""`(empty string) and NaN (Not a number), @Kab Refer [Falsy values](https://stackoverflow.com/questions/19839952/all-falsey-values-in-javascript) — Naren Murali, Oct 14 '17 at 17:44

score 1 · Answer 1 · answered Oct 14 '17 at 17:44

1

You can do something like

if(fname && lname && zip){
   // your code
}

This will check for if fname, lname and zip are not (null, undefined, "", false, 0, NaN)

answered Oct 14 '17 at 17:44

Gautam

815
6
15

Thanks! I'll give it a shot and see if I can make it work. – Kab Oct 14 '17 at 17:51
pls mark it as answer if it solves your problem. Have a nice day :) – Gautam Oct 14 '17 at 18:04

score 0 · Answer 2 · answered Oct 14 '17 at 17:46

0

As mentioned by Rohitas Behera in the comments if(variable) is enough.

if(variable) will not pass when variable is either of the following: * null * undefined * false (boolean value). * empty string

One common problem with using if(variable) is that you still want the if statement to pass if the variable is an empty string as it's some times a legit case. In these cases you can do.

if(variable || variable === '')

answered Oct 14 '17 at 17:46

Fyllekanin

274
1
12

Thank you for the advice. I'll keep it in mind as I attempt to finish the script. – Kab Oct 14 '17 at 17:51
OP want's non-null, so they should use `if(variable !== null)` as I stated in the comments. Using `if(variable)` is incorrect. `false`, empty strings, etc, are not `null`. – Spencer Wieczorek Oct 14 '17 at 22:14

How to create an if statement that checks the values variables are all non-null?

2 Answers2