How to check for empty value in Javascript

Question

I am working on a method of retrieving an array of hidden inputs in my form like so   lt input type  hidden  value  12 34 00  name  timetemp0  gt   lt input type  hidden  value  14 45 00  name  timetemp1  gt   lt input type  hidden  value  15 12 00  name  timetemp2  gt   lt input type  hidden  value  16 42 12  name  timetemp3  gt   lt input type  hidden  value  16 54 56  name  timetemp4  gt   lt input type  hidden  value  17 03 10  name  timetemp5  gt    My javascript function retrieves these individually by using getElementsByName  timetemp  i       for  i   i  lt  counter 0  value  i                finds hidden element by using concatenation of base name plus counter  var timetemp   document getElementsByName  timetemp  i      if there is a value alert that value to user - this is just for testing purposes at the moment   because there is only one of timetemp i then it occupies position 0 in array             if  timetemp 0  value    null                                alert   No value                               else                               alert  timetemp 0  value                      So what should happen is it will alert the user of the value in that hidden input but if it comes accross an input with no value like this    lt input type  hidden  value    name  timetemp16  gt    Then it will say  No value   However th if function cannot seem to work with this   I have tried     timetemp 0  value    null   timetemp 0  value     null   timetemp 0  value    undefined   timetemp 0  value          It always seems to default to else clause   Any ideas

User · Answer

Your script seems incorrect in several places.

Try this

var timetemp = document.getElementsByTagName('input');

for (var i = 0; i < timetemp.length; i++){
    if (timetemp[i].value == ""){
        alert ('No value');
    }
    else{
        alert (timetemp[i].value);
    }
}

Example: http://jsfiddle.net/jasongennaro/FSzT2/

Here's what I changed:

started by getting all the inputs via TagName. This makes an array
initialized i with a var and then looped through the timetemp array using the timetemp.length property.
used timetemp[i] to reference each input in the for statement

User · Answer

In my opinion  using  if value   to judge a value whether is an empty value is not strict  because the result of  v true false  is false when the value of v is 0 0 is not an empty value   You can use this function   const isEmptyValue    value    gt        if  value           value     null    value     undefined            return true       else           return false

User · Answer

The counter in your for loop appears incorrect  or we re missing some code   Here s a working Fiddle   This code     Where is counter 0  initialized  for  i   i  lt  counter 0  value  i      Should be replaced with   var timeTempCount   5    I m not sure where you re getting this value so I set it   for  var i   0  i  lt   timeTempCount  i

User · Answer

First  I would check what i gets initialized to  to see if the elements returned by getElementsByName are what you think they are  Maybe split the problem by trying it with a hard-coded name like timetemp0  without the concatenation  You can also run the code through a browser debugger  FireBug  Chrome Dev Tools  IE Dev Tools    Also  for your if-condition  this should suffice   if   timetemp 0  value           The value is empty    else          The value is not empty      The empty string in Javascript is a falsey value  so the logical negation of that will get you into the if-block

User · Answer

Comment as an answer   if  timetime 0  value    This works because any variable in JS can be evaluated as a boolean  so this will generally catch things that are empty  null  or undefined

[javascript] How to check for empty value in Javascript?

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