javascript之定时器的使用

一：什么是定时器

（一）无限循环定时器

<script>
    window.onload = function(){
       function test(){
           alert("test")
       }
        // 无限循环的执行函数test,间隔时间为2秒    
       setInterval(test,2000);
    }
</script>

（二）不循环执行定时器

<script>
    window.onload = function(){
       function test(){
           alert("test")
       }
        // 2秒后，执行test函数，只执行一次   
        setTimeout(test,2000);
    }
</script>

（三）开关定时器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>定时器</title>

<script>
    window.onload = function(){
        var oBtn1 = document.getElementById("btn1");
        var oBtn2 = document.getElementById("btn2");
        // 控制匿名函数
        var timer = null;
        oBtn1.onclick = function(){

            timer = setInterval(function(){
                alert("haha");
            },3000)
        }
        oBtn2.onclick = function(){
            clearInterval(timer);
        }
    }
</script>

</head>
<body>
    <input type="button" id="btn1" value="开启">
    <input type="button" id="btn2" value="关闭">
</body>
</html>

数码时钟

# 自己思路的代码

<!DOCTYPE html>

<head>

<style>

body{

font-size: 150px;

background:gray;

}

img{

100px;

height: 100px;

}

</style>

window.onload = function(){

var oData = new Date();

var h = oData.getHours().toString();

var m = oData.getMinutes().toString();

var s = oData.getSeconds().toString();

var oImg = document.getElementsByTagName("img")

function set(){

oImg[0].src = "pic/数字" + h[0] + ".png"

oImg[1].src = "pic/数字" + h[1] + ".png"

if(h.length==1){

oImg[0].src = "pic/数字0" + ".png"

oImg[1].src = "pic/数字" + h[0] + ".png"

}else{

}

oImg[0].src = "pic/数字" + h[0] + ".png"

oImg[1].src = "pic/数字" + h[1] + ".png"

if(m.length==1){

oImg[2].src = "pic/数字0" + ".png"

oImg[3].src = "pic/数字" + m[0] + ".png"

}else{

oImg[2].src = "pic/数字" + m[0] + ".png"

oImg[3].src = "pic/数字" + m[1] + ".png"

}

if(s.length==1){

oImg[4].src = "pic/数字0"+".png"

oImg[5].src = "pic/数字" + s[0]+".png"

}else{

oImg[4].src = "pic/数字" + s[0] + ".png"

oImg[5].src = "pic/数字" + s[1] + ".png"

}

set();

}

setInterval(window.onload,1000);

</script>

</head>

<body>

</body>

</html>

网上的做法

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>数字时钟</title>
<style>
body{
    font-size: 150px;
    background:gray;
}
img{
    width: 100px;
    height: 100px;
}
</style>

<script>

    function toDoule(n){
        if(n<10){
            return "0" + n    # 字符串和数字相加，会先将数字变成字符串，然后进行拼接
        }else{
            return "" + n
        }
    }
    window.onload = function(){
        var oImg = document.getElementsByTagName("img");
        function clock (){
            var oData = new Date();
            var toStr = toDoule(oData.getHours()) + toDoule(oData.getMinutes()) + toDoule(oData.getSeconds());
            for(var i=0; i<oImg.length;i++){
                oImg[i].src = "pic/数字" + toStr[i] + ".png"
            }
        }
        setInterval(clock,1000);
        // 这里调用，是为了一秒钟的延迟
        clock();
    }
</script>

</head>
<body>
    <img src="" alt="">
    <img src="" alt="">
    :
    <img src="" alt="">
    <img src="" alt="">
    :
    <img src="" alt="">
    <img src="" alt="">

</body>
</html>

潜在问题：ie7不支持 str[0] 这种写法取字符串的元素，因此要改成 str.chaAt(0) 解决兼容性问题

其他关于 Data的知识点

<script>
    
        var oData = new Date();
        // 获取几号
        alert(oData.getDate());
        // 0代表周日，国外从周日开始算
        alert(oData.getDay());
        // 获取年份s
        alert(oData.getFullYear());
        // 月份从0开始
        alert(oData.getMonth()+1);
    </script>

延时消失的提示框案例

自己思路

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>延时提示框</title>

    <style>
        #div1{
            width: 200px;
            height: 200px;
            background-color: red;
        }
        #div2{
            width: 200px;
            height: 200px;
            background-color:greenyellow;
            display: none;
        }
    </style>
    <script>
        window.onload = function(){
            var oDiv1 = document.getElementById("div1")
            var oDiv2 = document.getElementById("div2")
            function tools(){
                oDiv2.style.display = "none";
            }
            oDiv1.onmouseover = function(){
                oDiv2.style.display = "block";
            }
            oDiv1.onmouseout = function(){
                setTimeout(tools,2000);
            }
        } 
    </script>

</head>
<body>
    <div id="div1"></div>
    <div id="div2"></div>
</body>
</html>

网上做法：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>延时提示框</title>

    <style>
    
        #div1{
            width: 200px;
            height: 200px;
            background-color: red;
        }
        #div2{
            width: 200px;
            height: 200px;
            background-color:greenyellow;
            display: none;
        }
    </style>
    <script>
        window.onload = function(){
            var oDiv1 = document.getElementById("div1")
            var oDiv2 = document.getElementById("div2")
            // 用来存储定时器
            var timer = null;
            function tools(){
                oDiv2.style.display = "none";
            };
            oDiv1.onmouseover = function(){
                clearTimeout(timer);
                oDiv2.style.display = "block";
            };
            oDiv1.onmouseout = function(){
                // 如果要清除定时器，这里最好有一个变量接收定时器对象
                timer = setTimeout(tools,2000);
            };
            oDiv2.onmouseover = function(){
                // clearTimeout(tools)
                // 这里要清除的是定时器的对象，而不是函数
                clearTimeout(timer);
            };
            oDiv2.onmouseout = function(){
                timer = setTimeout(tools,500);
            }
        }
  
    </script>

</head>
<body>
    <div id="div1"></div>
    <div id="div2"></div>
</body>
</html>

无缝滚动案例

原理：修改left的值

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>无缝滚动</title>

    <style>
        #div1{
            width: 200px;
            height: 200px;
            background-color: red;
            position: absolute;
            left: 0;
            top: 20px;
        }
    </style>
    <script>

        window.onload = function(){
            var oDiv = document.getElementById("div1");
            setInterval(function(){
                // offsetLeft不仅仅不考虑left,还考虑margin
                oDiv.style.left = oDiv.offsetLeft + 10 + "px";
            },200)
        }  
    </script>

</head>
<body>
    <div id="div1"></div>
</body>
</html>

缺点是：会一直往右移动，不会再回来

一个方向循环滚动，鼠标悬停暂停滚动，移出继续滚动

缺点：只能往一个方向滚动

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>div中图片问题</title>

    <style>
    #div1 {
        border: 1px solid red;
        width: 1400px;
        height: 200px;
        position: relative;
        left: 50px;
　　　　 overflow:hidden;  # 超出部分隐藏

    }
    #div1 li{
        float: left;
        list-style: none;
        width: 200px;
        height: 200px;
    }
    #div1 ul{
        margin: 0;
        height: 200px;
        padding: 0;
        position: absolute;
        left: 0;
        top: 0;
    }
    </style>

    <script>
    window.onload = function(){
        var oDiv = document.getElementById("div1");
        var oUl = document.getElementById("ul1");
        var aLi = oUl.getElementsByTagName("li");
        var timer = null;
        // 这里很亮点，直接拼接两份
        oUl.innerHTML = oUl.innerHTML + oUl.innerHTML
        oUl.style.width = aLi[0].offsetWidth * aLi.length + "px"

        timer = setInterval(function(){
            oUl.style.left = oUl.offsetLeft  -2 + "px";
            if(oUl.offsetLeft < -oUl.offsetWidth/2){
                oUl.style.left = 0 + "px";
            }
        },30)
        // 鼠标悬停上去，停止滚动
        oDiv.onmousemove = function(){

            clearInterval(timer);

        }
        // 鼠标移开，又开始滑动
        oDiv.onmouseout = function(){

            timer = setInterval(function(){
            oUl.style.left = oUl.offsetLeft  -2 + "px";
            if(oUl.offsetLeft < -oUl.offsetWidth/2){
                oUl.style.left = 0 + "px";
            }
        },30)
        }
    }
    
    
    
    
    </script>

</head>
<body>
        <div id="div1">
                <ul id="ul1">
                    <li><img src="pic/美女1.jpg" alt=""></li>
                    <li><img src="pic/美女2.jpg" alt=""></li>
                    <li><img src="pic/美女3.jpg" alt=""></li>
                    <li><img src="pic/美女4.jpg" alt=""></li>
                    <li><img src="pic/美女5.jpg" alt=""></li>
                    <li><img src="pic/美女6.jpg" alt=""></li>
                    <li><img src="pic/美女7.jpg" alt=""></li>
                </ul>
        </div>
        <a href="#">左</a>
        <a href="#">右</a>
</body>
</html>

无缝滚动，增加向左，向右按钮

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>div中图片问题</title>

    <style>
    #div1 {
        border: 1px solid red;
        width: 1400px;
        height: 200px;
        position: relative;
        left: 50px;
        /* 超出的隐藏 */
        overflow: hidden;
    }
    #div1 li{
        float: left;
        list-style: none;
        width: 200px;
        height: 200px;
    }
    #div1 ul{
        margin: 0;
        height: 200px;
        padding: 0;
        position: absolute;
        left: 0;
        top: 0;
    }
    </style>

    <script>
    window.onload = function(){
        var oDiv = document.getElementById("div1");
        var oUl = document.getElementById("ul1");
        var aLi = oUl.getElementsByTagName("li");
        var timer = null;
        var speed = 3;
        // 这里很亮点，直接拼接两份
        oUl.innerHTML = oUl.innerHTML + oUl.innerHTML
        oUl.style.width = aLi[0].offsetWidth * aLi.length + "px"

        var oArr = document.getElementsByTagName("a")

        timer = setInterval(function(){
            oUl.style.left = oUl.offsetLeft  + speed + "px";
            if(oUl.offsetLeft < -oUl.offsetWidth/2){
                oUl.style.left = 0 + "px";
            }
            if(oUl.offsetLeft > 0){
                oUl.style.left = -oUl.offsetWidth/2 + "px";

            }
        },30)
        // 鼠标悬停上去，停止滚动
        oDiv.onmousemove = function(){
            clearInterval(timer);
        }
        // 鼠标移开，又开始滑动
        oDiv.onmouseout = function(){

            timer = setInterval(function(){
            oUl.style.left = oUl.offsetLeft  + speed + "px";
            if(oUl.offsetLeft < -oUl.offsetWidth/2){
                oUl.style.left = 0 + "px";
            }
            if(oUl.offsetLeft > 0){
                oUl.style.left = -oUl.offsetWidth/2 + "px";
            }
        },30)
        }

        oArr[0].onclick = function(){
            speed = -3
        }
        oArr[1].onclick = function(){
            speed = 3
        }

    }
    
    
    
    
    </script>

</head>
<body>
        <div id="div1">
                <ul id="ul1">
                    <li><img src="pic/美女1.jpg" alt=""></li>
                    <li><img src="pic/美女2.jpg" alt=""></li>
                    <li><img src="pic/美女3.jpg" alt=""></li>
                    <li><img src="pic/美女4.jpg" alt=""></li>
                    <li><img src="pic/美女5.jpg" alt=""></li>
                    <li><img src="pic/美女6.jpg" alt=""></li>
                    <li><img src="pic/美女7.jpg" alt=""></li>
                </ul>
        </div>
        <a href="#">左</a>
        <a href="#">右</a>
</body>
</html>

# TODO

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原文地址：https://www.cnblogs.com/meloncodezhang/p/12078079.html