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I want to try to do string call equivalent to the C# String.IsNullOrEmpty(string) in javascript. I looked online assuming that there was a simple call to make, but I could not find one.

For now I am using a if(string === "" || string === null) statement to cover it, but I would rather use a predefined method (I keep getting some instances that slip by for some reason)

What is the closest javascript (or jquery if then have one) call that would be equal?

I want to try to do string call equivalent to the C# String.IsNullOrEmpty(string) in javascript. I looked online assuming that there was a simple call to make, but I could not find one.

For now I am using a if(string === "" || string === null) statement to cover it, but I would rather use a predefined method (I keep getting some instances that slip by for some reason)

What is the closest javascript (or jquery if then have one) call that would be equal?

• javascript
• jquery

Share Improve this question Follow edited Sep 7, 2013 at 16:10 Daniele Armanasco 7,4511010 gold badges4545 silver badges5858 bronze badges asked Apr 21, 2011 at 16:23 SoatlSoatl 10.6k2828 gold badges100100 silver badges156156 bronze badges 2

• possible duplicate of What is the best way to test for an empty string with jquery-out-of-the-box? – Daniel A. White Commented Apr 21, 2011 at 16:28
• 3 @DanielA.White the argument is the same but, for a C# developer like me, this question (with its title) is more likely to be found – Daniele Armanasco Commented Sep 7, 2013 at 15:58

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9 Answers 9

Sorted by: Reset to default 234

You're overthinking. Null and empty string are both falsey values in JavaScript.

if(!theString) {
 alert("the string is null or empty");
}

Falsey:

• false
• null
• undefined
• The empty string ''
• The number 0
• The number NaN

If, for whatever reason, you wanted to test only null and empty, you could do:

function isNullOrEmpty( s ) 
{
    return ( s == null || s === "" );
}

Note: This will also catch undefined as @Raynos mentioned in the comments.

If you know that string is not numeric, this will work:

if (!string) {
  .
  .
  .

if (!string) {
  // is emtpy
}

What is the best way to test for an empty string with jquery-out-of-the-box?

You can create one Utility method which can be reused in many places such as:

 function isNullOrEmpty(str){
    var returnValue = false;
    if (  !str
        || str == null
        || str === 'null'
        || str === ''
        || str === '{}'
        || str === 'undefined'
        || str.length === 0 ) {
        returnValue = true;
    }
    return returnValue;
  }

you can just do

if(!string)
{
  //...
}

This will check string for undefined, null, and empty string.

To be clear, if(!theString){//...} where theString is an undeclared variable will throw an undefined error, not find it true. On the other hand if you have: if(!window.theString){//...} or var theString; if(!theString){//...} it will work as expected. In the case where a variable may not be declared (as opposed to being a property or simply not set), you need to use: if(typeof theString === 'undefined'){//...}

My preference is to create a prototype function that wraps it up for you.

Since the answer that is marked as correct contains a small error, here is my best try at coming up with a solution. I have two options, one that takes a string, the other takes a string or a number, since I assume many people are mixing strings and numbers in javascript.

Steps: -If the object is null it is a null or empty string. -If the type is not string (or number) it's string value is null or empty. NOTE: we might throw an exception here as well, depending on preferences. -If the trimmed string value has a length that is small than 1 it is null or empty.

var stringIsNullOrEmpty = function(theString)
{
    return theString == null || typeof theString != "string" || theString.trim().length < 1;
}

var stringableIsNullOrEmpty = function(theString)
{
    if(theString == null) return true;
    var type = typeof theString;
    if(type != "string" && type != "number") return true;
    return theString.toString().trim().length < 1;
}

you can say it by logic

Let say you have a variable name a strVal, to check if is null or empty

if (typeof (strVal) == 'string' && strVal.length > 0) 
{
// is has a value and it is not null  :)
}
else
{
//it is null or empty :(
}

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