代码如下：

<!DOCTYPE html>
<html>
<head>
    <title>111</title>
</head>
<body>
    <select id='bbb' title="1111">
        <option></option>
        <option value="b2">b2</option>
        <option value="b3">b3</option>
    </select>
</body>
<script type="text/javascript">
    // 添加事件
    var bbb = document.getElementById('bbb');
    if(bbb.addEventListener){
        bbb.addEventListener('change', function(){
            console.log('aaaaaa');
        });
    }
    else{
        bbb.attachEvent('onchange', function(){
            console.log('aaaaaa');
        });
    }

    // 设置select默认值
    bbb.value = 'b3';

    // 手动触发事件
    if (bbb.fireEvent){
        bbb.fireEvent('onchange');
    }
    else{
        ev = document.createEvent("HTMLEvents");  
        ev.initEvent("change", false, true);  
        bbb.dispatchEvent(ev);  
    }

    // jquery触发
    // bbb.trigger('change');

</script>
</html>