JavaScript - select change event in pure JavaScript

http://stackoverflow.com/questions/24172963/jquery-change-method-in-vanilla-javascript

by katalin_2003

HTML

<select id="Email">
    <option value=""></option>
    <option value="Test 1">Test 1</option>
    <option value="Test 2">Test 2</option>
</select>
<input id="UserName" type="text" />

JavaScript

function addEventHandler(elem, eventType, handler) {
    if (elem.addEventListener) {
        elem.addEventListener(eventType, handler, false);
    } else if (elem.attachEvent) {
        elem.attachEvent('on' + eventType, handler);

    }
}

addEventHandler(document, 'DOMContentLoaded', function () {
    addEventHandler(document.getElementById('Email'), 'change', function () {
        document.getElementById('UserName').value = this.value;
    });
});