JavaScript事件小例子

event.clientX在可视区中,鼠标点击的x坐标

event.clientY在可视区中,鼠标点击的y坐标

  示例:

<html lang="en"><head>

    <meta charset="UTF-8">

    <title>Documenttitle>

    <script type="text/javascript">

        document.onclick = function  () {

            alert(event.clientX +',' + event.clientY);

        }

    script>head><body>

body>html>

  示例:一个跟随鼠标指针移动的红色块



JavaScript事件小例子_第1张图片

 

<html lang="en"><head>

    <meta charset="UTF-8">

    <title>title>

    <style type="text/css">

        #div {

            width:100px;

            height:100px;

            background-color:red;

            position: absolute;

        }

 

    style>

    <script type="text/javascript">

        // 鼠标移动时触发改事件

        document.onmousemove = function  (ev) {

 

            // 获取距离文档顶部的高度

            var oScrollTop = document.documentElement.scrollTop ||document.body.scrollTop;

            // 获取距离文档左边的的宽度

            var oScrollLeft = document.documentElement.scrollLeft ||document.body.scrollLeft;

 

            // 获取鼠标事件

            var oEvent = event || ev;

            // 获取到div

            var oDiv = document.getElementById('div');

 

            // 设置div的位置

            oDiv.style.left = oEvent.clientX + oScrollLeft +'px';

            oDiv.style.top = oEvent.clientY + oScrollTop +'px';

 

        }

    script>head><body>

 

    <div id = "div">div>

body>html>

  示例:一串跟着鼠标走的div



JavaScript事件小例子_第2张图片

<html lang="en"><head>

    <meta charset="UTF-8">

    <title>title>

    <style type="text/css">

        #div {

            width:10px;

            height:10px;

            background-color:red;

            position: absolute;

        }

 

    style>

    <script type="text/javascript">

        // 鼠标移动时触发改事件

        window.onload = function  () {

 

            var oDivs = document.getElementsByTagName('div');

 

            document.onmousemove = function  (ev) {

                var oEvent = ev || event;

 

                oDivs[0].style.left = oEvent.clientX+'px';

                oDivs[0].style.top = oEvent.clientY+'px';

 

                for (var i = oDivs.length-1; i >0; i--) {

                    oDivs[i].style.left = oDivs[i-1].style.left;

                    oDivs[i].style.top = oDivs[i-1].style.top;

 

                };

 

 

            }

 

 

        }

    script>head><body>

 

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

        <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

        <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

        <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

        <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

    <div id = "div">div>

 

body>html>

键盘事件

• keyCode获取用户按下键盘的哪个按键

  如:键盘控制DIV移动

• ctrlKey 返回boolean值,按下时为true

• shiftKey 返回boolean值,按下时为true

• altKey 返回boolean值,按下时为true

  示例:用提示框将用户按的按键提示出来:

JavaScript事件小例子_第3张图片

<html lang="en"><head>

    <meta charset="UTF-8">

    <title>Documenttitle>

    <script type="text/javascript">

        // 按动键盘时触发事件

        document.onkeydown = function (ev) {

            var oEvent = ev || event;

            // 获取到按动的是哪个按键

            alert(oEvent.keyCode);

        }

    script>head><body>

body>html>

  示例:通过上下左右按键控制DIV的移动

JavaScript事件小例子_第4张图片

<html lang="en"><head>

    <meta charset="UTF-8">

    <title>Documenttitle>

    <style type="text/css">

        #div1 {

            width:100px;

            height:100px;

            left:10px;

            top:10px;

            background-color: gray;

            position: absolute;

        }

    style>

 

    <script type="text/javascript">

        document.onkeydown = function  (ev) {

            var oEvent = ev || event;

            var oDiv = document.getElementById('div1');

 

            if (oEvent.keyCode == 37) {

                oDiv.style.left =  oDiv.offsetLeft -10 +'px';

            }else if (oEvent.keyCode==38) {

                oDiv.style.top = oDiv.offsetTop -10 +'px';

            }else if (oEvent.keyCode == 39) {

                oDiv.style.left = oDiv.offsetLeft +10 +'px';

            }else if (oEvent.keyCode == 40) {

                oDiv.style.top = oDiv.offsetTop +10 +'px';

            };

        }

 

    script>head><body>

    <div id = "div1"> div>body>html>

  示例:按住control+enter键,提交留言框中的文字到留言板中


<html lang="en"><head>

    <meta charset="UTF-8">

    <title>Documenttitle>

 

    <script type="text/javascript">

        window.onload = function  () {

            var oText1 = document.getElementById('text1');

            var oText2 = document.getElementById('text2');

            var oBtn = document.getElementById('btn');

 

            // 鼠标点击提交按钮。进行留言

            oBtn.onclick =function  () {

                //点击提交按钮后,把留言框中的文字提交在留言区

                oText1.value += oText2.value +'\n';

                // 清空留言框

                oText2.value ='';

            };    

 

            // 按下control+enter按钮,进行留言,因为当前焦点在留言框中,所以事件要加载留言框中

            oText2.onkeydown =function  (ev) {

                var oEvent = ev || event;

 

                // 按下回车键和control键

                if (oEvent.keyCode == 13 && oEvent.ctrlKey) {

                    //点击提交按钮后,把留言框中的文字提交在留言区

                oText1.value += oText2.value +'\n';

                // 清空留言框

                oText2.value ='';

                };

            }

        }

    script>head><body>

    <textarea id = 'text1' roes = '10' cols = '40'>textarea>

    <br />

 

    <input type = "text" id = 'text2'/>

    <input type="button" value = '提交' id = 'btn'/>

 

body>html>

事件冒泡

  子标签发生事件后,向父级发送该事件,一直追溯到document。如:点击一个嵌套在body中的button,则该button的onclick事件也会传递给body、document中,触发他们的onclick里触发的函数.

  示例:

    

    <html lang="en">

    <head>

    <meta charset="UTF-8">

    <title>title>

    <style type="text/css">

        div {

            width:100px;

            height:100px;

            background-color: red;

            display: none;

        }

    style>

 

 

    <script type="text/javascript">

        window.onload = function () {

 

            var oBtn = document.getElementById('button');

            var oDiv = document.getElementById('div');

 

            // 点击buton后,button的事件会被触发

            oBtn.onclick =function() {

                oDiv.style.display ='block';

                alert("button被点击了");

            }

 

            // 由于事件冒泡,作为父级的document的onclick事件也会被触发

            document.onclick = function() {

 

                oDiv.style.display ='none';

                alert("document被点击了")

            }

        }

    script>

    head>

    <body>

    <input type = "button" value = "显示" id = "button">

    <div id = "div">div>

 

    body>

    html>

取消冒泡

  由于事件冒泡会触发父级的相关方法,所以我们经常会“取消事件冒泡”。

  取消事件冒泡的方法:event.cancelBubble=true

    

    <html lang="en">

    <head>

        <meta charset="UTF-8">

    <title>title>

    <style type="text/css">

        div {

            width:100px;

            height:100px;

            background-color: red;

            display: none;

        }

    style>

 

 

    <script type="text/javascript">

        window.onload = function () {

 

            var oBtn = document.getElementById('button');

            var oDiv = document.getElementById('div');

 

            // 点击buton后,button的事件会被触发

            oBtn.onclick =function(ev) {

                oDiv.style.display ='block';

                alert("button被点击了");

                // 在这里取消事件冒泡,防止事件向父级传递

                // 兼容性考虑,有的浏览器的事件并不是'event',所以把点击事件作为参数传递过来

                var oEvent = ev || event;

                oEvent.cancelBubble=true;

 

            }

 

            // 由于事件冒泡,作为父级的document的onclick事件也会被触发

            document.onclick = function() {

 

                oDiv.style.display ='none';

                alert("document被点击了")

            }

        }

    script>

    head>

    <body>

    <input type = "button" value = "显示" id = "button">

    <div id = "div">div>

 

    body>

    html>

事件的默认行为

  浏览器自带的行为就是默认行为

阻止默认行为

  只要将默认的事件return false,就可以组织默认行为的执行。

  示例:自定义右键菜单:默认的右键菜单是系统提供的选项,我们可以阻止默认的右菜单,来自定义新右键菜单样式

<html lang="en"><head>

    <meta charset="UTF-8">

    <title>title>

    <style type="text/css">

        ul {

            list-style-type: none;

            display:none;

            position:absolute;

        }

        * {

            margin:0;

            padding:0;

        }

    style>

    <script type="text/javascript">

 

        // 鼠标右键触发的时间

        document.oncontextmenu = function  (ev) {

            var oUl = document.getElementById('ul1');

            var oEvent = ev || event;

            oUl.style.display ='block';

 

            oUl.style.left = oEvent.clientX +'px';

            oUl.style.top = oEvent.clientY +'px';

 

            return false;

        }

 

        // 鼠标左键触发的事件

        document.onclick  = function  (ev) {

            var oUl = document.getElementById('ul1');

            oUl.style.display ='none';

 

        }

    script>head><body>

 

    

    <ul id = 'ul1' >

        <li>首页li>

        <li>登录li>

        <li>注册li>

    ul>

body>html>

  示例:输入框中只能输入数字和退格

<html lang="en"><head>

    <meta charset="UTF-8">

    <title>Documenttitle>

    <script type="text/javascript">

        window.onload = function  () {

            var oText = document.getElementById('text');

            oText.onkeydown =function  (ev) {

                var oEvent = ev || event;

                if ( (oEvent.keyCode < 40 && oEvent.keyCode !=8) || oEvent.keyCode >57 ) {

                    return false;

                };

 

            }

        }

    script>head><body>

    <input type = "text"  id = "text">

body>html>

拖拽

  拖拽时,鼠标经历三个事件:

• onmousedown 鼠标按下时,存储当前鼠标距离拖拽对象左上角的距离

• onmousemove 鼠标移动时,根据鼠标移动的距离移动拖拽对象的位置

• onmouseup 鼠标抬起时,停止拖拽

  示例:鼠标拖拽一个div

JavaScript事件小例子_第5张图片



<html lang="en"><head>

    <meta charset="UTF-8">

    <title>Documenttitle>

    <style type="text/css">

        #div1 {

            width:100px;

            height:100px;

            background-color: red;

            position: absolute;

        }

    style>

 

    <script type="text/javascript">

        window.onload = function  () {

 

            var oDiv = document.getElementById('div1');

            // 当鼠标按下时计算鼠标距离div左上角的位置

            oDiv.onmousedown =function  (ev) {

                var oEvent = ev || event;

                var oX = oEvent.clientX - oDiv.offsetLeft;

                var oY = oEvent.clientY - oDiv.offsetTop;

 

                // 当鼠标开始移动,重新设置div的位置

                document.onmousemove = function  (ev) {

                    var oEvent = ev || event;

                    oDiv.style.left = oEvent.clientX - oX +'px';

                    oDiv.style.top = oEvent.clientY - oY +'px';

 

                };

 

                // 当鼠标抬起,结束移动,清除移动事件的函数

                document.onmouseup = function  () {

                    document.onmousemove = null;

                    document.onmouseup = null;

                };

 

 

            };

 

        };

    script>head><body>

    <div id = "div1">div>body>html>

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