<script>
    var h = prompt("(倒三角)请输入欲打印的行数","");
    if(h<=0){
        h=12;
    }
    for(var i=h;i>0;i--){
        if(i%2==0){
            var color="red";
        }else{
            var color="blue";
        }
        document.write("<hr size='5' color='"+color+"' width='"+i+"%'>");
    }
</script>