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

Answer 1

try this:

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

Answer 2

$('#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

• Raynos: 10 seconds. You must have cheated.
• Naveed Ahmad: @Raynos - Please there is no race here. We all here to help each other. There is no competition.
• hunter: @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: @Hunter 8 answers? What's going on. @NaveedAhman there is a race. I have to beat Hunter!
• Flexo - Save the data dump: @hunter I read it as intended to be quite a light-hearted comment

Answer 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.

• hunter: you would still need to use val() not value()
• Brandon McKinney: Edited from value() to val().

Answer 4

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

Answer 5

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

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

Answer 6

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.

• d4nt: Fixed, I was typing too fast!

Answer 7

Try:

if(myStr){
 // Your code here
}

• hunter: if there were a "Reject" option this would def win