0/example/cr.1.html

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
<button id="btn">click</button>
<script>

    var addEvent1 = function (el, type, fn, capture) {
        if (window.addEventListener) {
            el.addEventListener(type, fn, capture);
        }
        else {
            el.attachEvent('on' + type, fn);
        }
    };

    var addEvent = (function () {
        if (window.addEventListener) {
            return function (el, type, fn, capture) {
                el.addEventListener(type, fn, capture);
            }
        }
        else {
            return function (el, type, fn) {
                var IEtype = 'on' + type;
                el.attachEvent(IEtype, fn);
            }
        }
    })();
    var btn = document.getElementById('btn');
    addEvent1(document.getElementById('btn'), 'click', function (e) {
        console.log(e);
        alert(1);
    });

    console.log(addEvent);
</script>
</body>
</html>