попробуйте так
<html>
<head>
<style>
</style>
</head>
<body>
<span id="num">50</span>
<div class="wish wadd"> link </div>
<div class="wish wdell"> link </div>
<div class="wish wadd"> link </div>
<div class="wish wdell"> link </div>
<div class="wish wadd"> link </div>
<div class="wish wdell"> link </div>
<div class="wish wadd"> link </div>
<div class="wish wdell"> link </div>
<script>
var f = function(event){
event.preventDefault()
if(/wadd/.test(this.className)) {this.clicked = false; num.innerHTML = (+num.innerHTML) - 1; return}
this.clicked = true; num.innerHTML = (+num.innerHTML) + 1
}
;[].forEach.call(document.querySelectorAll("div.wish"),function(d){
d.addEventListener("click", f)
})
</script>
</body>
</html>