How do I test for a empty string/null, using JavaScript?

Question

How do I test for a input[text] field that has nothing in?

This is what I have so far:

    if ($('#StartingPrice').length == ""){
        alert("ERROR!");
    }

Any help would be greatly appreciated, Thanks

Naftali · Accepted Answer · 2011-04-21 15:58:59Z

8

try this:

if ($('#StartingPrice')[0].value.length == 0){
    alert("ERROR!");
}

answered Apr 21, 2011 at 15:58

Naftali

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Comments

hunter · Accepted Answer · 2011-04-21 16:12:03Z

8

$('#StartingPrice').length returns an integer so it will never equal "".

Try using the val() method:

if($('#StartingPrice').val() == "")
{
    alert("ERROR!");
}

.length

The number of elements in the jQuery object.

.val()

Get the current value of the first element in the set of matched elements.

.value

No Such jQuery Method Exists

edited Apr 21, 2011 at 16:12

answered Apr 21, 2011 at 15:58

hunter

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6 Comments

Raynos Over a year ago

10 seconds. You must have cheated.

Naveed Ahmad Over a year ago

@Raynos - Please there is no race here. We all here to help each other. There is no competition.

hunter Over a year ago

@Naveed thank you for standing up for me, some times users like Raynos can make people sad, but I try to stay positive, mostly through meditation and deep breathing.

Raynos Over a year ago

@Hunter 8 answers? What's going on. @NaveedAhman there is a race. I have to beat Hunter!

Flexo - Save the data dump Over a year ago

@hunter I read it as intended to be quite a light-hearted comment

|

Brandon McKinney · Accepted Answer · 2011-04-21 16:16:56Z

3

Just as an alternative to the already provided solutions... you could also use a Regex to test that it actually contains something other than whitespace.

!!$('#StartingPrice').val().match(/\S/)

This will test for the existing of a non-whitespace character and using the Not-Not will convert it to a Boolean value for you. True if it contains non-whitespace. False if blank or only whitespace.

edited Apr 21, 2011 at 16:16

answered Apr 21, 2011 at 16:04

Brandon McKinney

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2 Comments

hunter Over a year ago

you would still need to use val() not value()

Brandon McKinney Over a year ago

Edited from value() to val().

alexl · Accepted Answer · 2011-04-21 16:00:05Z

2

if ($('#StartingPrice').val() === ""){
    alert("ERROR!");
}

answered Apr 21, 2011 at 16:00

alexl

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Comments

Raynos · Accepted Answer · 2011-04-21 15:58:18Z

1

if ($('#StartingPrice').val() == ""){
    alert("ERROR!");
}

If the value of your text input is any empty string then it's empty.

answered Apr 21, 2011 at 15:58

Raynos

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Comments

d4nt · Accepted Answer · 2011-04-21 16:01:23Z

1

I think you want this:

if ($('#StartingPrice').val() == false) {
    alert("Error!");
}

Use the .val() method to get the value and then pass that into the if. If the string is empty or white space it will evaluate to false.

answered Apr 21, 2011 at 16:01

d4nt

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1 Comment

d4nt Over a year ago

Fixed, I was typing too fast!

LooPer · Accepted Answer · 2011-04-21 15:59:08Z

-3

Try:

if(myStr){
   // Your code here
}

answered Apr 21, 2011 at 15:59

LooPer

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1 Comment

hunter Over a year ago

if there were a "Reject" option this would def win

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