Form field validation verify checkbox using JavaScript

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Topic: Form field validation - verify checkbox using JavaScript

WebSpider
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posts:	147
joined:	06/29/2006
from:	Seattle, WA

posted on: 08/01/2006 09:58:56 PM

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Form field validation - verify checkbox using JavaScript

It is very common to see if a checkbox has been checked or not before a form being sent out to server. This can be done by the following javascript code

<script language="JavaScript">
function verify_checkbox(checkbox)
{
   var isChecked = false;
   if checkbox[0]) { /* chackbox group/array */
	
      for(var j=0; j<checkbox.length; j++){
         if(checkbox[j].checked){
	    alert("The checkbox #"+(j+1)+"has been checked.");
            isChecked = true;
         }
      }
   }else{
      if(checkbox.checked){
         alert("The checkbox has been checked.");
	 isChecked = true; 
      }
   }

   if(!isChecked)
   	alert("No checkbox has been checked.");

}
</script>

What we have learned are:

The attribute 'checked' of checkbox plays a key role;

There could be an array of checkboxes bearing the same group name.

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WebSpider
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posts:	147
joined:	06/29/2006
from:	Seattle, WA

posted on: 06/27/2011 06:02:27 PM

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The corresponding HTML should be as follows.

<html>
<body>
<form onsubmit="return verify_checkbox(this.checkbox);" action="">
    <input type="checkbox" id="checkbox" value="Dog">Dog</p>
    <input type="checkbox" id="checkbox" value="Cat">Cat</p>
    <input type="submit" value="Submit" />
</form>
</body>
</html>

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