经过document.getElementsByName来实现 复选框的全选，全部选，反选
<html>
<head><meta charset="utf-8"/></head>
<body>
<input type="checkbox" name="a"/>
<input type="checkbox" name="a"/>
<input type="checkbox" name="a"/>
<input type="checkbox" name="a"/>
<input type="checkbox" name="a"/>
<input type="checkbox" name="a"/>
<br>
<input type="button" value="全选" onclick="selectall()"/>
<input type="button" value="全不选" onclick="selectno()"/>
<input type="button" value="反选" onclick="r()"/>
</body>
<script>
function selectall()
{
for(i=0;i<document.getElementsByName("a").length;i++)
{
document.getElementsByName("a")[i].checked = "checked";
}
}
function selectno()
{
for(i=0;i<document.getElementsByName("a").length;i++)
{
document.getElementsByName("a")[i].checked = false;
}
}
function r()
{
for(i=0;i<document.getElementsByName("a").length;i++)
{
if(document.getElementsByName("a")[i].checked == false)
{
document.getElementsByName("a")[i].checked = "checked";
}
else document.getElementsByName("a")[i].checked = false;
}
}
</script>
<html>