JavaScript 图像地图
图像地图指的是带有可点击区域的图像。
实例
简单的 HTML 图像映射
本例演示一幅没有添加 JavaScript 的图像映射。
添加了 JavaScript 的图像映射
本例演示一幅添加了 JavaScript 的图像映射，当鼠标浮动于某个热点上时，会调用 JavaScript 函数来显示热点所对应的星球的简介。
JavaScript 图像地图
我们已经从 HTML 教程中了解到，图像地图是带有可点击区域的图像。通常情况下，每个区域是一个相关的超级链接。单击某个区域，就回到达相关的链接。
实例
下面的例子演示如何创建带有可点击区域的 html 图像地图：
<img src ="planets.gif" width ="145" height ="126"
alt="Planets"usemap ="#planetmap" />
<map id ="planetmap" name="planetmap">
<area shape ="rect" coords ="0,0,82,126" href ="sun.htm" target ="_blank"
alt="Sun" />
<area shape ="circle" coords ="90,58,3" href ="mercur.htm" target ="_blank"
alt="Mercury" />
<area shape ="circle" coords ="124,58,8" href ="venus.htm" target ="_blank"
alt="Venus" />
</map>
alt="Planets"usemap ="#planetmap" />
<map id ="planetmap" name="planetmap">
<area shape ="rect" coords ="0,0,82,126" href ="sun.htm" target ="_blank"
alt="Sun" />
<area shape ="circle" coords ="90,58,3" href ="mercur.htm" target ="_blank"
alt="Mercury" />
<area shape ="circle" coords ="124,58,8" href ="venus.htm" target ="_blank"
alt="Venus" />
</map>
添加 JavaScript
我们可向图像地图内部的 <area> 标签添加（能调用JavaScript的）事件。<area> 标签支持以下事件：onClick、onDblClick、onMouseDown、onMouseUp、onMouseOver、onMouseMove、onMouseOut、onKeyPress、onKeyDown、onKeyUp、onFocus和onBlur。
这是添加了 JavaScript 的上面的例子：
<html>
<head>
<script type="text/javascript">
function writeText(txt)
{
document.getElementById("desc").innerHTML=txt
}
</script>
</head>
<body>
<img src="planets.gif" width="145" height="126"
alt="Planets" usemap="#planetmap" />
<map id ="planetmap" name="planetmap">
<area shape ="rect" coords ="0,0,82,126"
planets like Jupiter are by far the largest objects
in our Solar System.')"
href ="sun.htm" target ="_blank" alt="Sun" />
<area shape ="circle" coords ="90,58,3"
difficult to study from the Earth because it is
always so close to the Sun.')"
href ="mercur.htm" target ="_blank" alt="Mercury" />
<area shape ="circle" coords ="124,58,8"
often considered a twin sister to the Earth because
Venus is the nearest planet to us, and because the
two planets seem to share many characteristics.')"
href ="venus.htm" target ="_blank" alt="Venus" />
</map>
<p id="desc"></p>
</body>
</html>
<head>
<script type="text/javascript">
function writeText(txt)
{
document.getElementById("desc").innerHTML=txt
}
</script>
</head>
<body>
<img src="planets.gif" width="145" height="126"
alt="Planets" usemap="#planetmap" />
<map id ="planetmap" name="planetmap">
<area shape ="rect" coords ="0,0,82,126"
onMouseOver="writeText('The Sun and the gas giantplanets like Jupiter are by far the largest objects
in our Solar System.')"
href ="sun.htm" target ="_blank" alt="Sun" />
<area shape ="circle" coords ="90,58,3"
onMouseOver="writeText('The planet Mercury is verydifficult to study from the Earth because it is
always so close to the Sun.')"
href ="mercur.htm" target ="_blank" alt="Mercury" />
<area shape ="circle" coords ="124,58,8"
onMouseOver="writeText('Until the 1960s, Venus wasoften considered a twin sister to the Earth because
Venus is the nearest planet to us, and because the
two planets seem to share many characteristics.')"
href ="venus.htm" target ="_blank" alt="Venus" />
</map>
<p id="desc"></p>
</body>
</html>