判断浏览器是IE的几种方式

<script>
if(!+[1,])alert("这是ie浏览器");
　　 else alert("这不是ie浏览器");
</script>

 <script>
    //if(!+"\v1")alert("+"\v1"判断是IE浏览器"); //此方式未成功
</script>

<script>
    if(!!(window.attachEvent && navigator.userAgent.indexOf('Opera') === -1))
    alert("IE浏览器！");
</script>

<script>
    if(!!(!window.addEventListener&& navigator.userAgent.indexOf('Opera') === -1))
    alert("是IE浏览器！");
    if(!!(document.all && navigator.userAgent.indexOf('Opera') === -1))
    alert("是IE！");
</script>