javascript控制光标移动

<input  type=button  value="<"  onclick=go(-1)>   

<input  id=demo  value="press  button">

<input  type=button  value=">"  onclick=go(1)>   

<script>

function  go(n){

demo.focus();

with(document.selection.createRange()){moveStart("character",n);collapse();select();}

}

</script>