Javascript form validation problems

Question

Alright, so I feel my issue is that of a really simple one. basically, I'v created a website, and am trying to use javascript to validate input, all of which initially was one. When input fields were left blank, an error would prompt and so forth. I haven't changed a single thing, and now no form of validation takes place, and it simply ignores my javascript. Any ideas?

Here's an example of the Javascript;

function validate(el){
var alphabets="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ";
var temp;

if (el.Full_Name.value == "") {
     alert("Cannot leave area field blank!");
     return false;
 }
}

for (var i=0;i<el.Full_Name.value.length;i++){
temp=el.Full_Name.value.substring(i,i+1)
if (alphabets.indexOf(temp)==-1){
alert("Sorry, your name contains a " + temp +", which is not allowed.")
return false
   }
  }

Here's the HTML:

<form name="testform" onSubmit="return validate(testform)">
<table width="650" border="0">

<tr>
 <td width="79" valign="top">
  <label for="Full_Name">Full Name<span class="required_star"> * </span></label>
 </td>
 <td width="289" valign="top">
  <input size="15" type="text" name="Full_Name" id="Full_Name" maxlength="50" value="" />
 </td>
</tr>
<tr>
 <td colspan="4" style="text-align:center">
  <input type="submit" value="Proceed"/>
 </td>
</tr></table>
</form>

I don't seem to be getting any errors in the console. It's just really frustrating me that it worked, and now all of a sudden, unless i accidentally changed something without realising — Philip Newton
– Philip Newton, Commented Sep 14, 2015 at 0:53
document.form.Full_Name.value should be document.forms.testform.Full_Name.value. document.forms is a collection, you can access the members by name (if they have one) or index (the form you seek seems to be the first, so document.forms[0]). — RobG
– RobG, Commented Sep 14, 2015 at 1:03

sinisake · Accepted Answer · 2015-09-14 01:01:46Z

2

You can speed up/simplify things, a bit:

<form name="testform" onSubmit="return validate(this)">

Notice use of 'this' - it actually refers to form element itself...

JS:

 function validate(el) {
if (el.Full_Name.value == "") {
     alert("Cannot leave area field blank!");
     return false;
 }
}

Demo: http://jsfiddle.net/tv9hntkL/

P.S. Correct selector in your case, would be: (document.testform.Full_Name.value == "")

edited Sep 14, 2015 at 1:01

answered Sep 14, 2015 at 0:55

sinisake

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6 Comments

Philip Newton Over a year ago

Thanks for the response! I just tried to implement this as you have done, and still no luck. On selection of the submit button it just proceeds as if theres no javascript whatsoever

sinisake Over a year ago

@Philip Newton, One syntax error (at least), check it now: jsfiddle.net/tv9hntkL/1 Redundant closing bracket '}' was problem....

Philip Newton Over a year ago

Worked absolutely incredibly. Just one more follow question if it's alright? If i wanted to validate that the user's input was lets say, more than 5 characters long, how would i go about doing that?

sinisake Over a year ago

Np, glad it worked, finally. To limit length, you can do something like this: jsfiddle.net/tv9hntkL/2

Philip Newton Over a year ago

You've been exceptionally helpful! I don't want to bother you with another question, but i feel it is necessary hahah! If i later wanted to input radio buttons, or the likes of a drop-down menu, is validation possible for this?

|

Petros Kyriakou · Accepted Answer · 2015-09-14 00:36:33Z

1

You are accessing the form input wrong.

var myForm =  document.forms.<form-name>;
myForm.<input-name>.value; // holds the value of a certain input

will give you access to the value correctly.

answered Sep 14, 2015 at 0:36

Petros Kyriakou

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2 Comments

Philip Newton Over a year ago

Thanks for the quick response. I implemented alike the way you suggested, and still nothing: document.forms.testform.Full_Name.value=="".

Petros Kyriakou Over a year ago

please provide your HTML in your original post.

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