4.定时器

定时器：id=setInterval(fun,30); 清除定时器：clearInterval(id);

延时：id=setTimeOut(fun,30); 清除延时：clearTimeOut(id);

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str.toCharAt(i);获取字符串str第i个位置上的字符；兼容ie和高级浏览器；

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例子：简易时钟；

function toDou(n)
{
    if(n<10)
    {
        return '0'+n;
    }
    else
    {
        return ''+n;
    }
}

window.onload=function ()
{
    var aImg=document.getElementsByTagName('img');
    
    function tick(){
        var oDate=new Date();
        
        var str=toDou(oDate.getHours())+toDou(oDate.getMinutes())+toDou(oDate.getSeconds());
        
        for(var i=0;i<aImg.length;i++)
        {
            aImg[i].src='img/'+str.charAt(i)+'.png';
        }
    }
    setInterval(tick, 1000);
    tick();
};

字符串连接：str=''+n;

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无缝滚动：

window.onload=function ()
{
    var oDiv=document.getElementById('div1');
    var oUl=oDiv.getElementsByTagName('ul')[0];
    var aLi=oUl.getElementsByTagName('li');
    
    oUl.innerHTML=oUl.innerHTML+oUl.innerHTML;
    oUl.style.width=aLi[0].offsetWidth*aLi.length+'px';
    
    function move(){
        if(oUl.offsetLeft<-oUl.offsetWidth/2)
        {
            oUl.style.left='0';
        }
        if(oUl.offsetLeft>0)
        {
            oUl.style.left=-oUl.offsetWidth/2+'px';
        }
        oUl.style.left=oUl.offsetLeft+2+'px';
    }
    var timer=setInterval(move, 30);
    
    oDiv.onmouseover=function ()
    {
        clearInterval(timer);
    };
    
    oDiv.onmouseout=function ()
    {
        timer=setInterval(move, 30);
    };
};

oUl.innerHTML+=oUl.innerHTML;

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延时提示框：

window.onload=function ()
{
    var oDiv1=document.getElementById('div1');
    var oDiv2=document.getElementById('div2');
    var timer=null;
    
    oDiv2.onmouseover=oDiv1.onmouseover=function ()
    {
        clearTimeout(timer);
        oDiv2.style.display='block';
    };
    oDiv2.onmouseout=oDiv1.onmouseout=function ()
    {
        timer=setTimeout(function (){
            oDiv2.style.display='none';
        }, 500);
    };
};