知识点2

http://www.runoob.com/w3cnote/front-end-interview-a-few-important-points-of-knowledge.html

<!-- 如何快速打乱一个数组 -->

<script>
var arr = [1,2,3,4,5,6,7,8,9];
arr.sort(function(){
return Math.random() - 0.5;
})
console.log(arr)
</script>

// 判断移动端设备
function deviceType(){
    var ua = navigator.userAgent;
    var agent = ["Android", "iPhone", "SymbianOS", "Windows Phone", "iPad", "iPod"];    
    for(var i=0; i<len,len = agent.length; i++){
        if(ua.indexOf(agent[i])>0){         
            break;
        }
    }
}
deviceType();
window.addEventListener('resize', function(){
    deviceType();
})


// 判断微信浏览器
function isWeixin(){
    var ua = navigator.userAgent.toLowerCase();
    if(ua.match(/MicroMessenger/i)=='micromessenger'){
        return true;
    }else{
        return false;
    }
}

浏览器兼容不好，不建议使用。