js对金额的完美处理

<INPUT TYPE="text" style="ime-mode:disabled" onkeydown="if(event.repeat)event.returnValue=false;//屏蔽连按" onkeypress="initPrice(this)" onblur="checkinp(this)">
  <SCRIPT LANGUAGE="JavaScript">
  <!--
    function initPrice(oInput){
        var num = oInput.value;
        /* 取光标位置 */
        var s = document.selection.createRange();
        var r = oInput.createTextRange();
        s.setEndPoint( "StartToStart",r);
        var curP = s.text.length;

        num = num.substring(0,curP) + String.fromCharCode(event.keyCode) + num.substring(curP);
        var reg = /^\-?([\d\,]*\.?\d{0,3}?)?$/;
        // 0~9:48~57; \,:44; \-:45; \.:46;
        if ( event.keyCode<44 || event.keyCode>57 || event.keyCode==47 || !reg.test(num) ) {
            if (event.keyCode==46) curP = num.indexOf(".")+1;
            event.returnValue = false;
        }
        else {
            curP += 1;
            if (num=="-") return;
            if (/\.\d{3}$/.test(num)) num = num.substring(0,num.length-1);
            event.returnValue = false;
            num = num.replace(/,/g,"");
            num = parseFloat(num).toFixed(2);
            var re = /(-?\d+)(\d{3})/;
            while(re.test(num)){
               num = num.replace(re,"$1,$2")
            }
            oInput.value=num;
            if(num.indexOf(".")>0 && curP <= num.indexOf(".") ) curP = num.indexOf(".");
        }
        //恢复光标位置
        r.moveStart( 'character',curP);
        r.collapse(true);
        r.select();
    }
    function checkinp(obj){
            var num = obj.value.replace(/,/g,"");
            num = parseFloat(num).toFixed(2);
            var re = /(-?\d+)(\d{3})/;
            while(re.test(num)){
               num = num.replace(re,"$1,$2")
            }
            obj.value=num;
    }
  //-->
  </SCRIPT>