Non Negative Number Validation

I'm trying to have a user enter 4 numbers that are nonzero and non-negative.
This is what I have so far...

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 var intList = new Array(4); 

var i=0; 

for (i=0; i<4; i++) 

{ 

intList[i]=prompt('Enter an integer',' '); 

    if(!intList[i]<=0)

        {

        return false;

        } else {

        return true;

        }

}

Not sure why it isn't working

Sep 27 '07 #1

Subscribe Post Reply

6404

pbmods

5,821

Expert 4TB

Heya, Lonsalot. Welcome to TSDN!

Please use CODE tags when posting source code:

[CODE=javascript]
JavaScript code goes here.
[/CODE]

Couple of issues to tackle:

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 if(!intList[i]<=0)

        {

        return false;

        } else {

        return true;

        }

Aside from the fact that this line does exactly the same thing:

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return( intList[i] <= 0 );

Your code is returning *false* if intList[i] > 0 (or ! <= 0, same thing).

And by *returning*, you break out of the loop.

A better method would be to continue to prompt the User until he enters a valid value (but allow him to cancel out of it).

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for( var i = 0; i < 4; ++i )

{

    do

    {

        var int = prompt('Enter a number greater than zero:', 1);
 
        if( int === false )

        {

            return int;

        }

    }

    while( int <= 0 );
 
    intList[i] = int;

}

Sep 28 '07 #2

lonsalot

When I load the page, nothing happens. I'm not sure what is wrong

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<html>

<head>

<title>Average Function</title>
 
<script language="javascript" type="text/javascript">
 
var intList = new Array(4); 

var i=0; 

for( var i = 0; i < 4; ++i )

{

    do

    {

        var int = prompt('Enter a number greater than zero:', 1);
 
        if( int === false )

        {

            return int;

        }

    }

    while( int <= 0 );
 
    intList[i] = int;

}
 
var a = parseInt(intList[0]);  //not sure if this is neccessary???

var b = parseInt(intList[1]);

var c = parseInt(intList[2]);

var d = parseInt(intList[3]);
 
var avg = (a + b + c + d)/4;
 
alert(avg);
 
</script>

</head>

<body>

</body>

</html>

Sep 28 '07 #3

lonsalot

What does this statement mean?

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if( int === false )

Sep 28 '07 #4

dmjpro

2,476

2GB

What does this statement mean?

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if( int === false )

It is strict comparison.
As JavaScript is loosely typed language.
See the tutorial of JavaScript internal conversion :-)

Kind regards,
Dmjpro.

Sep 28 '07 #5

pbmods

5,821

Expert 4TB

Heya, Lonsalot.

To build on what DMJPro mentioned, if the User presses 'Cancel' at the prompt, then the value of int will be false.

The problem with, for example, doing this:

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if( int == false )

is that 0 would also resolve to false, which would break out of the loop. This would not be ideal behavior, so instead we use:

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if( int === false )

to ensure that we only break the loop if the User clicks on the Cancel button.

Random, but I thought I might as also well mention:

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var intList = new Array(4);

This creates a new Array and sets the value of the first element to 4. It does not create an Array with 4 elements. In JavaScript, you do not need to know how big your variables will be when you create them.

Now then.

If you're getting a blank page, the code is probably generating an error. In which browser are you testing this script?

Sep 28 '07 #6

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