checking if value is null using jQuery

Question

I'm trying to check if the value of my variable is null but it does not work. And i also have to stop script and don't insert the row

Html

<input type="text" name="for_intitule" id="form_intitule">

Jquery

var form_intitule = $('input[name=form_intitule]').val();

if(form_intitule == null){
  alert('fill the blank');
  return false;
}

UPDATE :

$('#insertForm').on('click', function(){
  var form_intitule = $('input[name=form_intitule]').val();

  if($('input[name=form_intitule]').val().trim().length == 0){
    alert('fill the blank');
  }
  $.ajax({
    type: "GET",
    url: "lib/function.php?insertForm="+insertForm+"&form_intitule="+form_intitule,
    dataType : "html",
    error: function(XMLHttpRequest, textStatus, errorThrown) {
      alert(XMLHttpRequest + '--' + textStatus + '--' + errorThrown);
    },
    success:function(data){
    }
  });
});

If you put a breakpoint in your browser at the `if` statement line, what is the value of `form_intitule` when the input box is blank? — krillgar, Feb 09 '16 at 13:49
The `.val()` always returns a string. You can check if the string is empty using: `.val().trim().length == 0`. — Praveen Kumar Purushothaman, Feb 09 '16 at 13:50
@PraveenKumar It's kinda puzzling that you closed this as a duplicate of unrelated question and then give a completely different answer — JJJ, Feb 09 '16 at 13:54
@PraveenKumar Yeah well perhaps it's better to use your own judgement instead of blindly closing questions because there happens to be something in a list — JJJ, Feb 09 '16 at 14:01

score 5 · Accepted Answer · answered Feb 09 '16 at 14:00

5

The .val() always returns a string. You can check if the string is empty using:

.val().trim().length == 0

So your full condition will be:

var form_intitule = $('input[name=form_intitule]').val().trim();

if (form_intitule.length == 0) {
  alert('fill the blank');
  return false;
}

answered Feb 09 '16 at 14:00

Praveen Kumar Purushothaman

164,888
24
203
252

tank you, it's working but my value is inserted .. – Lucas Frugier Feb 09 '16 at 14:04
@LucasFrugier Put it in the `submit` event while you `return false`. Can you show the full code? Thanks. – Praveen Kumar Purushothaman Feb 09 '16 at 14:06
my post is updated :) – Lucas Frugier Feb 09 '16 at 14:09
@LucasFrugier You forgot to add the `return false` after the alert. Oops. – Praveen Kumar Purushothaman Feb 09 '16 at 14:16
oh :o my bad ! thank you – Lucas Frugier Feb 09 '16 at 14:18
@LucasFrugier Ha ha... $h!t happens! `:)` – Praveen Kumar Purushothaman Feb 09 '16 at 14:19

score 0 · Answer 2 · answered Feb 09 '16 at 14:06

0

I would suggest a safer method

var formElement = $('input[name=form_intitule]');
if ($(formElement).length == 0 || $(formElement).val().trim().length == 0) {
   console.log("element does not exist OR value is empty");
}

answered Feb 09 '16 at 14:06

Devaffair

182
14

checking if value is null using jQuery

2 Answers2