How to check if a variable is null or empty string or all whitespace in JavaScript?

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I need to check to see if a variable is null or has all empty spaces or is just blank ("").

I have the following, but it is not working:

var addr;
addr = "  ";

if (!addr) {
    // pull error 
}

If I do the following, it works:

if (addr) {

}​

What I need is something like the C# method String.IsNullOrWhiteSpace(value).

A non-jQuery solution that more closely mimics IsNullOrWhiteSpace, but to detect null, empty or all-spaces only:

function isEmptyOrSpaces(str){
    return str === null || str.match(/^ *$/) !== null;
}

...then:

var addr = '  ';

if(isEmptyOrSpaces(addr)){
    // error 
}

* EDIT * Please note that op specifically states:

I need to check to see if a var is null or has any empty spaces or for that matter just blank.

So while yes, "white space" encompasses more than null, spaces or blank my answer is intended to answer op's specific question. This is important because op may NOT want to catch things like tabs, for example.

Check for an empty string in javascript, I need to check to see if a variable is null or has all empty spaces or is just blank (​""). Possible duplicate of How do you check for an empty string in JavaScript? Related Questions & Answers; How to create a thread without implementing the Runnable interface in Java? How to read the data from a properties file in Java?

You can use if(addr && (addr = $.trim(addr)))

This has the advantage of actually removing any outer whitespace from addr instead of just ignoring it when performing the check.

Reference: http://api.jquery.com/jQuery.trim/

Javascript test a string to see if it is Null or Whitespace. Equivelent to , If we need to check whether there's any value, we can do. if (strValue) { //. } If we want to check specifically for an empty string over null, We would think  Javascript test a string to see if it is Null or Whitespace.

if (addr == null || addr.trim() === ''){
  //...
}

A null comparison will also catch undefined. If you want false to pass too, use !addr. For backwards browser compatibility swap addr.trim() for $.trim(addr).

How to check empty/undefined/null string in JavaScript , Thanks! But I'd like to attach it to String, so that I could use it like this: if('hello'.​isNullOrWhiteSpace()){ alert('Empty'); }else{ alert('Not empty'); }  Check undefined, null, empty or blank variable in JavaScript While working with jQuery or JavaScript, if you don’t know whether a variable exists (that means, if it was declared) you should check with the   typeof  operator.

You can create your own method Equivalent to

String.IsNullOrWhiteSpace(value)

function IsNullOrWhiteSpace( value) {

    if (value== null) return true;

    return value.replace(/\s/g, '').length == 0;
}

C#, If we want to check any string either it is filled or empty we can use Javascript for such purpose for How to check if a variable is an array in JavaScript? How to  Check string is null, empty, or only contains the white space characters in C# NET 2012 javascript validation textbox not allowed space disable asp.net 4.6 - Duration: Check if String is

isEmptyOrSpaces(str){
    return !str || str.trim() === '';
}

String.IsNullOrEmpty in JavaScript, HTML · CSS · JavaScript · PHP · JQuery A string will be null if it has not been assigned a value or has explicitly been Empty, or only contains white-space characters then return True otherwise return False. public static bool check( string str) Please write to us at contribute@geeksforgeeks.org to report any issue with  Is there a JavaScript equivalent to .NET's String.IsNullOrWhitespace so that I can check if a textbox on the client-side has any visible text in it? I'd rather do this on the client-side first than post back the textbox value and rely only on server-side validation, even though I will do that as well.

How to Check for an Empty String in JavaScript, In JS, an empty string is false. And !undefined is true, so that check isn't needed​. This checks if the type of the value is "string" (and thus non-null and not undefined), sloppy, would suffice, in which case you wouldn't need to define this function at all. If your intent is to use it as a function to pass in variables: String. The last scenario you may want to test is your variable has a value, it isn’t null or an empty string, but the “value” only consists of spaces. For example, you may have a CSV file that the author accidentally entered a space in a column for which they didn’t intend to enter a value.

Check if a string is empty or null in Java, You can use the strict equality operator ( === ) to check whether a string is empty or not. The comparsion str === "" will only return true if the data type of the value  Its Javadoc documentation says as much: 'Checks if a String is not empty (""), not null and not whitespace only.'. The above approaches and variations on the above approaches can be used in Java to determine if a String is not null, not empty, and not white space only.

Groovy string isempty or null, In this post, we will discuss how to check if a string is empty or null in Java. isEmpty() method to check for an empty string in Java. All Problems · Array · Tree isBlank(String) method which additionally checks for whitespace as well. Java, Python, JavaScript, C#, PHP and many more popular programming languages. Checking for Null or Empty or White Space Only String in Java. We can verify whether the given string is empty using the isEmpty() method of the String class. This method returns true only if length() is 0.

Comments
  • Do you really mean has *any* empty spaces? Or do you mean is all empty spaces?
  • what about undefined?
  • Possible duplicate of How do you check for an empty string in JavaScript?
  • Whitespace can also include tabs, other kinds of spaces, etc. Use /^\s*$/ to catch those, too.
  • @Grant I purposefully did NOT do that because op said "I need to check to see if a var is null or has any empty spaces or for that matter just blank".
  • What about using test() instead of match()? return str === null || (/^ *$/).test(str);
  • @subsci Grant's suggestion would return a false-positive for a string containing tabs. Are you suggesting I change the name of the function? Ok.
  • @Madbreaks the op stated "What I need is something like this C# method: String.IsNullOrWhiteSpace". That method treats tabs as whitespace.
  • Assuming, of course the op wants to remove the whitespace. :)
  • Your answer will return a false positive if addr is intialized with e.g. an integer.