Javascript string comparison not detected

Question

Sure this is a simple problem but I am new to this. Am trying to develop a simple website for a user to work out a password and then if they get it right, take them to a congrats screen where they win a prize. However my if statement is not working in the code below

<script>
function CheckPassword() {
    var pword = document.getElementById("inpPassword").value;

    if (pword == ""|| pword == NULL) {
        alert("Please enter a password");
    } else if (pword == 'newman') {
        window.open('congratulations.html', '_self');
    } else {
        alert("Wrong password");    
    }
}
</script>

If I add an alert with the pword value then it prints out correctly what was entered. However the code picks up when the password input is blank, however if the input field is not blank then it does not go to the other screen or show the wrong password alert box. I have tried it with an alert box saying correct instead of the link to the new page but still did not work. Also tried using String(pword) in case that was the problem. Am sure this is a simple solution but just can't see it.

Thanks

Please provide the html to go with this so we can test your code. Also check the browser console I I suspect it will tell you the problem — musefan
– musefan, Commented Sep 21, 2017 at 12:49
Equivalent to if (pword == "" || pword == null) is if (!pword) — codtex
– codtex, Commented Sep 21, 2017 at 12:52

Durga · Accepted Answer · 2017-09-21 12:52:40Z

1

function CheckPassword() {
    var pword = document.getElementById("inpPassword").value;

    if (pword == ""|| pword == null){
        alert("Please enter a password");
    }
    else if (pword == 'newman') {
        window.open('congratulations.html', '_self');
    }
    else
    {
        alert("Wrong password");    
    }


}

<input type='password' id='inpPassword'>
<input type='button' onclick='CheckPassword()'>

if (pword == "" || pword == null) , its null not NULL . keywords are case sensitive.

answered Sep 21, 2017 at 12:52

Durga

15.6k2 gold badges31 silver badges55 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

P.S. · Accepted Answer · 2017-09-21 12:53:28Z

You should use null instead of NULL. Seems like it works besides of opening new window, because there is no congratulations.html in my snippet:

function CheckPassword() {
    var pword = document.getElementById("inpPassword").value;

    if (pword == ""|| pword == null){
        alert("Please enter a password");
    }
    else if (pword == 'newman') {
        window.open('congratulations.html', '_self');
    }
    else
    {
        alert("Wrong password");    
    }


}

<input id="inpPassword">
<button onclick="CheckPassword()">Click</button>

Kunvar Singh · Accepted Answer · 2017-09-21 12:54:02Z

You may try here:

The mistake was here, you wrote NULL instead of null, beacuse of javascript understand null as a reserve keyword.

And use === for hard checking(data as well type checking of variaable)

function CheckPassword() {
    var pword = document.getElementById("inpPassword").value;

    if (pword == ""|| pword == null){
        alert("Please enter a password");
    }
    else if (pword === 'newman') {
        alert('congratulations.html', '_self');
    }
    else
    {
        alert("Wrong password");    
    }
}

<input type="" name="a" id="inpPassword">
<input type="button" onClick="CheckPassword()" value="check">

musefan · Accepted Answer · 2017-09-21 12:56:22Z

It seems the problem is when you compare to NULL. If you check your browser console you will likely get the following error:

Uncaught ReferenceError: NULL is not defined

That is not the correct syntax for null checks, it will look for a variable called "NULL" which you don't have. You should use null (lowercase) instead:

if (pword == ""|| pword == null){

The full adjusted code is as follows:

function CheckPassword() {
    var pword = document.getElementById("inpPassword").value;

    if (pword == ""|| pword == null) {
        alert("Please enter a password");
    } else if (pword == 'newman') {
        window.open('congratulations.html', '_self');
    } else {
        alert("Wrong password");    
    }
}

Here is a working example.

Faly · Accepted Answer · 2017-09-21 12:52:41Z

0

Null, "" are equivalent to false in Javascript. You just have to:

    if (!pword) {
        alert("Please enter a password");
    } else if (pword === 'newman'){
        window.open('congratulations.html', '_self');        
    } else {           
        alert("Wrong password");   
    }

answered Sep 21, 2017 at 12:52

Faly

13.4k2 gold badges21 silver badges39 bronze badges

Comments

Bhargav Chudasama · Accepted Answer · 2017-09-21 13:01:02Z

0

you can write null in small case so its work

function CheckPassword() {
var pword = document.getElementById("inpPassword").value;

if (pword == "" || pword == null ) {
  alert("Please enter a password");
} else if (pword == 'newman') {
  window.open('congratulations.html', '_self');
} else {
  alert("Wrong password");
}
}

<input id="inpPassword" onblur="CheckPassword()">

edited Sep 21, 2017 at 13:01

answered Sep 21, 2017 at 12:53

Bhargav Chudasama

7,2256 gold badges24 silver badges41 bronze badges

1 Comment

rookief1ain Over a year ago

Thanks for all your help. Works fine now,

Collectives™ on Stack Overflow

Javascript string comparison not detected

6 Answers 6

Comments

Comments

Comments

Comments

Comments

1 Comment

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

Comments

Comments

Comments

Comments

Comments

1 Comment

Related