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

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 == "" || 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 => !b.includes(x));
 if(conditions.includes(a)|| (typeof a === 'string' && 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) && 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_

function empty (a,b=[]){
if(!Array.isArray(b)) return;
conditions=[null,'0','0.0',false,undefined,''].filter(x => !b.includes(x));
if(conditions.includes(a)|| 
(['string', 'number'].includes(typeof a) && 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_

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_

function empty (a,b=[]){
    if(!Array.isArray(b)) return;

    conditions=[null,'0','0.0',false,undefined,''].filter(x => !b.includes(x));
    if(Array.isArray(a) && a.length > 0){
    for (i = 0; i < a.length; i++) { if (empty(a[i],b))return true;} 
    } 
    
    if(conditions.includes(a)|| 
    (['string', 'number'].includes(typeof a) && 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_

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.

User · Answer

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

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

User · Answer

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

User · Answer

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

User · Answer

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

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

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

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

User · Answer

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

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

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