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Question

Javascript: How to check if a string is empty?

Answer 1

A:

if (value == "") {
  // it is empty
}

Ray 2010-03-04 17:41:57

If value is really a string, then this is correct, but it will also return true, if value = false or 0 or null. use === instead.

Residuum 2010-03-04 17:43:26

@Residuum: The question reads “How to check if a string is empty?”

Gumbo 2010-03-04 17:44:35

@Gumbo: An answer that works under all circumstances is in my opinion better than an answer that provides the bare minimum, so I agree with Residuum. Things like that are especially important to point out for a beginner.

OregonGhost 2010-03-04 17:47:50

@Gumbo: As the question suggests, the questioner is not experienced in Javascript. And as Javascript is not a strongly typed language, it is a common source of error to not explicitly check for type as well. Been there, done that.

Residuum 2010-03-04 17:48:42

Answer 2

+2 A:

This should work:

if (variable === "") {

}

Tom Castle 2010-03-04 17:42:12

If variable is really a string, then this is correct, but it will also return true, if variable = false or 0 or null. use === instead.

Residuum 2010-03-04 17:44:00

You're quite right, it would be safer to use ===. Edited.

Tom Castle 2010-03-04 17:45:03

Answer 3

A:

if (mystring == '') alert('string is empty');

kekekela 2010-03-04 17:44:21

Answer 4

+4 A:

If you want to know if it's an empty string use === instead of ==.

if(variable === "") {
}

This is because === will only return true if the values on both sides are of the same type, in this case a string.

for example: (false == "") will return true, and (false === "") will return false.

nxt 2010-03-04 17:46:29

Answer 5

+1 A:

I check length.

if (str.length == 0) {
}

Dustin Laine 2010-03-04 17:46:39

Answer 6

A:

But for a better check:

if(str == "" || str == null)
{
    //enter code here
}

Christopher Richa 2010-03-04 17:49:53

a null variable will have a length of 0, so why not use the length rather than two comparisons.

Dustin Laine 2010-03-04 18:04:21

Actually I was going to edit this before it got closed: if(!str || str == "") { //enter code here }There are many ways to do this, but a String is not necessarily null if it has "" in it. Empty is **not** null.

Christopher Richa 2010-03-04 18:35:17

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Javascript: How to check if a string is empty?

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