How to check if a value is not null and not empty string in JS

Question

Is there any check if a value is not null and not empty string in Javascript  I m using the following one   var data    get its value from db  if data    null  amp  amp  data                do something     But I m wondering if there is another better solution  Thanks

User · Answer

I got so fed up with checking for null and empty strings specifically  that I now usually just write and call a small function to do it for me          Test if the given value equals null or the empty string          param  string  value     const isEmpty    value    gt  value     null    value             Test  isEmpty                true isEmpty null           true isEmpty 1              false isEmpty 0              false isEmpty undefined      false

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If you truly want to confirm that a variable is not null and not an empty string specifically  you would write   if data     null  amp  amp  data                 do something     Notice that I changed your code to check for type equality             If  however you just want to make sure  that a code will run only for  reasonable  values  then you can  as others have stated already  write   if  data         do something     Since  in javascript  both null values  and empty strings  equals to false  i e  null    false    The difference between those 2 parts of code is that  for the first one  every value that is not specifically null or an empty string  will enter the if  But  on the second one  every true-ish value will enter the if  false  0  null  undefined and empty strings  would not

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Both null and empty could be validated as follows    lt script gt  function getName        var myname   document getElementById  Name   value      if myname        amp  amp  myname    null           alert  My name is   myname        else          alert  Please Enter Your Name

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I often test for truthy value and also for empty spaces in the string   if    data    data trim   length     0          do something here     If you have a string consisting of one or more empty spaces it will evaluate to true

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Both null and an empty string are falsy values in JS  Therefore    if  data            is completely sufficient   A note on the side though  I would avoid having a variable in my code that could manifest in different types  If the data will eventually be a string  then I would initially define my variable with an empty string  so you can do this   if  data                   without the null  or any weird stuff like data    0   getting in the way

User · Answer

Instead of using  if data     null  amp  amp  data          amp  amp  data   undefined        do something     You can use below simple code  if Boolean value        do something       Values that are intuitively    empty     like 0  an empty string  null  undefined  and NaN  become false Other values become true

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When we code empty in essence could mean any one of the following given the circumstances   0 as in number value 0 0 as in float value  0  as in string value  0 0  as in string value null as in Null value  as per chance it could also capture  undefined or it may not undefined as in undefined value false as in false truthy value  as per chance 0 also as truthy but what if we want to capture false as it is    empty sting value with no white space or tab            string with white space or tab only  In real life situation as OP stated we may wish to test them all or at times we may only wish to test for limited set of conditions  Generally if  a  return true   serves its purpose most of the time however it will not cover wider set of conditions  Another hack that has made its round is return   value    value    undefined    value     quot  quot     value length    0   But what if we need control on whole process  There is no simple whiplash solution in native core JavaScript it has to be adopted  Considering we drop support for legacy IE11  to be honest even windows has so should we  below solution born out of frustration works in all modern browsers   function empty  a b       if  Array isArray b   return    var conditions  null  0   0 0  false undefined     filter x   gt   b includes x     if conditions includes a     typeof a      string   amp  amp  conditions includes a toString   trim        return true     return false      Logic behind the solution is function has two parameters a and b  a is value we need to check  b is a array with set conditions we need to exclude from predefined conditions as listed above  Default value of b is set to an empty array     First run of function is to check if b is an array or not  if not then early exit the function  next step is to compute array difference from  null  0   0 0  false undefined     and from array b  if b is an empty array predefined conditions will stand else it will remove matching values  conditions    predefined set  -  to be excluded set  filter function does exactly that make use of it  Now that we have conditions in array set all we need to do is check if value is in conditions array  includes function does exactly that no need to write nasty loops of your own let JS engine do the heavy lifting  Gotcha if we are to convert a into string for comparison then 0 and 0 0 would run fine however Null and Undefined would through error blocking whole script  We need edge case solution  Below simple    covers the edge case if first condition is not satisfied  Running another early check through include makes early exit if not met  if conditions includes a        string    number   includes typeof a   amp  amp  conditions includes a toString   trim       trim   function will cover for wider white spaces and tabs only value and will only come into play in edge case scenario  Play ground  x000D   x000D  function empty  a b      if  Array isArray b   return  conditions  null  0   0 0  false undefined     filter x   gt   b includes x    if conditions includes a        string    number   includes typeof a   amp  amp  conditions includes a toString   trim        return true     return false     console log  1   empty     console log  2   empty       console log  3   empty             console log  4   empty 0    console log  5   empty  0     console log  6   empty 0 0    console log  7   empty  0 0     console log  8   empty false    console log  9   empty null    console log  10   empty null  null     console log  11 dont check 0 as number   empty 0   0      console log  12 dont check 0 as string   empty  0    0      console log  13 as number for false as value  empty false  false     x000D   x000D   x000D   Lets make it complex - what if our value to compare is array its self and can be as deeply nested it can be  what if we are to check if any value in array is empty  it can be an edge business case   x000D   x000D  function empty  a b          if  Array isArray b   return       conditions  null  0   0 0  false undefined     filter x   gt   b includes x        if Array isArray a   amp  amp  a length  gt  0       for  i   0  i  lt  a length  i      if  empty a i  b  return true                    if conditions includes a            string    number   includes typeof a   amp  amp  conditions includes a toString   trim            return true             return false         console log  checking for all values   empty  1  0      console log  excluding for 0 from condition   empty  1  0      0      x000D   x000D   x000D   it simple and wider use case function that I have adopted in my framework   Gives control over as to what exactly is the definition of empty in a given situation Gives control over to redefine conditions of empty Can compare for almost for every thing from string  number  float  truthy  null  undefined and deep arrays Solution is drawn keeping in mind the resuability and flexibility  All other answers are suited in case if simple one or two cases are to be dealt with  However  there is always a case when definition of empty changes while coding above snippets make work flawlessly in that case

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try it----------   x000D   x000D  function myFun    x000D  var inputVal document getElementById  inputId   value  x000D  if inputVal   x000D  document getElementById  result   innerHTML   lt span style  color green  gt The value is   inputVal   lt  span gt    x000D    x000D  else  x000D  document getElementById  result   innerHTML   lt span style  color red  gt Something error happen  the input May be empty  lt  span gt    x000D    x000D    x000D   lt input type  text  id  inputId  gt  x000D   lt input type  button  onclick  myFun    value  View Result  gt  x000D   lt h1 id  result  gt  lt  h1 gt  x000D   x000D   x000D

User · Answer

if  data  trim   length  gt  0         use data     the    optional chaining operator will short-circuit and return undefined if data is nullish  null or undefined  which will evaluate to false in the if expression

User · Answer

x000D   x000D  function validateAttrs arg1  arg2  arg3 arg4       var args   Object values arguments       return  args filter x  gt  x   null     x   length lt  0   console log validateAttrs  1  2  3  4    console log validateAttrs  1  2  3  null    console log validateAttrs  1  undefined  3  4    console log validateAttrs  1  2      4    console log validateAttrs  1  2  3  null    x000D   x000D   x000D

[javascript] How to check if a value is not null and not empty string in JS

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