element.addEventListener返回“未定义”，而值应为“ Test”

Question

function appElement(element, return_value) {
var p = document.createElement('input');
p.setAttribute('type', 'button');
p.setAttribute('value', return_value);
element.appendChild(p);
element.addEventListener('click', function(event) {
    alert(this.value);
});}
return appElement(arguments[0]);

javaScriptDriver.ExecuteScript(_jsscript, new object[] { element, return_value });