CODEWITHSUNDEEP
javascript
Kraken
Kraken

Reputation: 24213

If (NULL), will it work?

Okay so i am using the following code.

 <html>
    <head>
    <link type="text/css" rel="stylesheet" href="html.css" />
    <script type="text/javascript">
    function getName()
    {

    if(name)
    alert("you thought i forgot you" + name + "?");
    else
    name=prompt("what's your name","here");


    }
    </script>
    </head>

    <body onload="var name;">
    <p onclick="getName()"; >click here</p>
    </body>
    </html>

Now if on clicking the <p> text first time it prompts me, and if I click cancel without entering my name, and then again click the <p> text, it doesnt prompt me anything,

instead it shows the name to be filled as NULL. now in C,

char a=NULL;
if(a)

evaluates to false, doesn't it happen in javascript?

Upvotes: 2

Views: 696

Answers (5)

beatgammit
beatgammit

Reputation: 20205

<html>
<head>
<link type="text/css" rel="stylesheet" href="html.css" />
<script type="text/javascript">
var name;

function getName() {
    console.log(name, typeof name);
    if(name && name !== 'null') {
        alert("you thought i forgot you" + name + "?");
    } else {
        name=prompt("what's your name","here");
    }
}
</script>
</head>

<body>
<p onclick="getName()"; >click here</p>
</body>
</html>

As you can see from the console output, name is a string with value null. This is pretty stupid, but I guess window.name stringifies the value, in this case null.

EDIT:

You probably shouldn't be using the word name as it's reserved (used as a property in window).

window.name returns a string value of whatever is stored in it. For example:

window.name = null;

window.name === 'null' true

window.name === null false

Upvotes: 0

6502
6502

Reputation: 114461

This is a tricky situation.

The identifier "name" is special for the global window object so you cannot use it reliably as a variable.

Using for example name$ your code works as expected.

Also I think that "onload" requires an expression, not a statement; so you cannot use it that way. Apparently works with name because that is predefined.

Upvotes: 1

Casey Chu
Casey Chu

Reputation: 25463

One thing you might be running into: when you set the global name, you are actually setting window.name. window.name is a special property that actually persists even after refreshing the page.

Try making a page with the script:

alert(window.name);
name = 'hello';

On the first run, it should alert "undefined". If you refresh the page, though, you should see "hello".

You can avoid the problem by renaming name to something else.

Upvotes: 4

Nathan
Nathan

Reputation: 6216

This fiddle behaves as you desire, I think: http://jsfiddle.net/YUCyL/5/

As you can see, I moved the variable declaration to the head and renamed it to username instead of "name".

Upvotes: 1

Rupok
Rupok

Reputation: 2082

try with this

if (name==undefined)
name=prompt("what's your name","here");
else
alert("you thought i forgot you" + name + "?");

Upvotes: 1

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