html - Trying to calculate the total price of items taking into account the quantity selected Javascript -

this first time posting on site. have webpage outlines 1 of products intent sell

here dilemma. have code asks user press + , - buttons quantity of item want. trying work out if user presses + or - number of times need able to take account number of clicks , calculate total price order on separate line. im new javascript appreciated thanks

 <form>    <br> item price: $463.50    <br> please select quantity    <input type='button' name='subtract' onclick='javascript:   document.getelementbyid("qty").value--;' value='-'/>    <input type='button' name='add' onclick='javascript: document.getelementbyid("qty").value++;' value='+'/>    <input type='text' name='qty' id='qty' />    </form> 

<form> <br> item price: $<span id='price'>463.50</span>       var unitprice = (document.getelementbyid('price').innertext || document.getelementbyid('price').textcontent);     var price = parsefloat(unitprice);     var count = parseint(document.getelementbyid("qty").value, 10)     var total = price * count;     alert(total); // or whatever want