This simple JS can't set the value of para. I guess getElementByName doesn't work. But why?

<script>

function fn()  

{   

    document.getElementById(para).setAttribute(name,hi);  

    document.getElementByName(hi).setAttribute(value,my value is high);  

}  

</script>

HTML:

<input type=button onClick=fn() value=click me>

<input id=para type=text />