<input type="button" value="a()" onclick="a()();" />
<script Language="Javascript">
<!--
function a(){
    var cnt = 0;
    return function(){
        alert(cnt);
        cnt = cnt + 1;
    }
}
// -->
</script>

<input type="button" value="b()" onclick="b();" />
<script Language="Javascript">
<!--
function b(){
　　a()();
    a()();
    a()();
}
// -->
</script>

<input type="button" value="c()" onclick="c();" />
<script Language="Javascript">
<!--
function c(){
    var d = a();
    d();
    d();
    d();
}
// -->
</script>

<input type="button" value="d()" onclick="d();" />
<script Language="Javascript">
<!--
function d(){
    var e = a();
    e();
    e();
    e();
    var f = a();
    f();
    f();
    f();
}
// -->
</script>