html - How to reset a counter back to 0 with a button in javascript? -

i have counter in javascript right , button adds 1 value counter, have far:

    var counter = 0;      var = 0;      var add = function(valuetoadd){          += valuetoadd;          document.getelementbyid('value').innerhtml = a;  		}

    value $<span id="value">0</span>       <button width="500" height="500" id = add class="button button1" onclick="javascript:add(1)">add value</button> 

i need button reset counter 0 appreciated.

add button, reset function , set values "0" shown in code below:

<button width="500" height="500" id ="reset" class="button button1" onclick="javascript:reset()">reset value</button>   <script type="text/javascript">    var reset= function(){     = 0;     document.getelementbyid('value').innerhtml = a;     } </script> 

btw declared var count = 0 in code (question) not using (apparently).