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<!DOCTYPE html>
<html>
<body>

<h3>A demonstration of how to access a MAP element</h3>

<img src="planets.gif" width="145" height="126" alt="Planets" usemap="#myMap">

<map id="myMap" name="myMap">
  <area shape="rect" coords="0,0,82,126" alt="Sun" href="sun.htm">
  <area shape="circle" coords="90,58,3" alt="Mercury" href="mercur.htm">
  <area shape="circle" coords="124,58,8" alt="Venus" href="venus.htm">
</map>

<p>Click the button to get the number of area elements in the image-map.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
    var x = document.getElementById("myMap").areas.length;
    document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>