Adding jQuery

Question

I am trying to add via jquery event and I get NaN. What am I missing?

<input type="hidden" id="skillcount" name="skillcount" value="3" onchange="valueadd(this)"/> function valueadd(ok){ var value=parseFloat($(this).val())+1; } 

Answer 1

The code should be:

 function valueadd(ok){ // "this" inside here refers to the window var value=parseFloat(ok.value)+1; } 

Inline onchange is actually an anonymous function:

 function() { //"this" inside here refers to the element valueadd(this); } 

So, "this" is an argument called "ok" in the scope of valueadd. However, as others have argued, you probably want to use jquery bind, so the "this" inside valueadd will point to an element.

Answer 2

this is a reserved word in JavaScript, so you cannot use it in the signature of a function argument.

I would probably change this code to ...

 $('#skillcount').change(function() { var value = parseFloat($(this).val()) + 1; }); 

jsFiddle .

... and release the inline event handler.

To check if parseFloat() returns NaN , use isNaN() .

Answer 3

You should do it just like this:

 <input type="hidden" id="skillcount" name="skillcount" value="3" onchange="valueadd()"/> function valueadd() { var value=parseFloat(this.value)+1; } 

Answer 4

• Assign your behavior with jQuery since you have this and use it anyway. Do not use built-in event handlers
• A function related to jQuery is executed in the scope of the element on which the event occurred. This means that this is an element.
• this cannot be used as a parameter name or anything other than to access an object in a scope.

Using:

 <input type="hidden" id="skillcount" name="skillcount" value="3" /> <script type="text/javascript"> $( '#skillcount' ).bind( 'change', function() { var value = parseFloat( $( this ).val() ) + 1; } ); </script>