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

Question

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

User · Answer

Old question  but I think it deservers a simpler answer  You can simply do  var addr    quot    quot    if  addr  amp  amp  addr trim           console log  quot I m not null  nor undefined  nor empty string  nor string composed of whitespace only  quot

User · Answer

You can try this   do      var op   prompt  please input operatot  n you most select one of   -           while  typeof op     object     op             execute block of code when click on cancle or ok whthout input

User · Answer

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

User · Answer

isEmptyOrSpaces str       return str     null    str trim   length gt 0

User · Answer

function isEmptyOrSpaces str       return str     null    str match     s n r          null

User · Answer

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

User · Answer

You can use if addr  amp  amp   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

User · Answer

Try this out          Checks the string if undefined  null  not typeof string  empty or space s       param  any  str string to be evaluated      returns  boolean  the evaluated result    function isStringNullOrWhiteSpace str        return str     undefined    str     null                                 typeof str      string                                  str match             null      You can use it like this  isStringNullOrWhiteSpace  Your String

User · Answer

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

User · Answer

isEmptyOrSpaces str       return  str    str trim

User · Answer

Simplified version of the above   from here  https   stackoverflow com a 32800728 47226   function isNullOrWhitespace  input       return  input     input trim

User · Answer

When checking for white space the c  method uses the Unicode standard  White space includes spaces  tabs  carriage returns and many other non-printing character codes  So you are better of using   function isNullOrWhiteSpace str       return str    null    str replace   s g      length  lt  1

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

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