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What's wrong with the following uncheck checkbox code?

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  What's wrong with the following uncheck checkbox code? justaguy <lichunshen84@gmail.com> - 2018-02-23 04:00 -0800
    Re: What's wrong with the following uncheck checkbox code? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2018-02-23 13:22 +0100
    Re: What's wrong with the following uncheck checkbox code? justaguy <lichunshen84@gmail.com> - 2018-02-23 05:45 -0800

#34739 — What's wrong with the following uncheck checkbox code?

For the following FORM, if for whatever reason the user has already checked the checkbox field with id of "sig" but its prior field's value is invalid, uncheck this checkbox. See below. However, the uncheck function fails.
document.getElementById('sig').checked = false;
Its syntax seems correct. Why?  Thanks.

<form>
enter promo code: 
<input type="text" id="code" name="code" onblur="verify(this)"> 
<span id="note" style="color:red"></span>

yes to include signature: <input type="checkbox" id='sig' name='sig' value=1>

<!-- other elements below -->
... 
<input type="submit" name='send'>
</form>

<script>
 var verify = function {
   if (this !== 'whatevercode') {
   // alert the user
   document.getElementById('note').innerHTML = 'Your promo code is invalid';

   // uncheck signature checkbox field
   document.getElementById('sig').checked = false;
  }

 }
</script>

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#34740

justaguy <lichunshen84@gmail.com> wrote on 23 Feb 2018 in
comp.lang.javascript: 

> 
> For the following FORM, if for whatever reason the user has already
> checked the checkbox field with id of "sig" but its prior field's value
> is invalid, uncheck this checkbox. See below. However, the uncheck
> function fails. document.getElementById('sig').checked = false;
> Its syntax seems correct. Why?  Thanks.
> 
> <form>
> enter promo code: 
> <input type="text" id="code" name="code" onblur="verify(this)"> 
> <span id="note" style="color:red"></span>
> 
> yes to include signature: <input type="checkbox" id='sig' name='sig'
> value=1> 

<input type="checkbox" id='sig' name='sig'> 

There should better be no "value=1" in your input checkbox,
if you want it checked by default, use 'checked'.

> <!-- other elements below -->
> ... 
> <input type="submit" name='send'>
> </form>
> 
> <script>
>  var verify = function {
>    if (this !== 'whatevercode') {


in input type="text"
'this' cannot be a string by itself,
as it is/points to a DOM-object.
so you could use this.value,
and in the function,
you have to reference this 'this', 
not write this 'this'.


onblur = "verify(this);"

 var verify = function(t) {
    	if (t.value !== 'whatevercode')
    	    	...
};

or

'use strict';
const verify = (t) => {
    	if (t.value !== 'whatevercode')
    	    	...
};


>    // alert the user
>    document.getElementById('note').innerHTML = 'Your promo code is
>    invalid'; 
> 
>    // uncheck signature checkbox field
>    document.getElementById('sig').checked = false;
>   }
> 
> }
> </script>
> 



-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#34741

On Friday, February 23, 2018 at 7:01:05 AM UTC-5, justaguy wrote:
> For the following FORM, if for whatever reason the user has already checked the checkbox field with id of "sig" but its prior field's value is invalid, uncheck this checkbox. See below. However, the uncheck function fails.
> document.getElementById('sig').checked = false;
> Its syntax seems correct. Why?  Thanks.
> 
> <form>
> enter promo code: 
> <input type="text" id="code" name="code" onblur="verify(this)"> 
> <span id="note" style="color:red"></span>
> 
> yes to include signature: <input type="checkbox" id='sig' name='sig' value=1>
> 
> <!-- other elements below -->
> ... 
> <input type="submit" name='send'>
> </form>
> 
> <script>
>  var verify = function {
>    if (this !== 'whatevercode') {
>    // alert the user
>    document.getElementById('note').innerHTML = 'Your promo code is invalid';
> 
>    // uncheck signature checkbox field
>    document.getElementById('sig').checked = false;
>   }
> 
>  }
> </script>

Yeah, the "this" reference of the element's value was my oversight.

Excellent. Thank you.

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