function check(form){
document.form.radio.checked = true;//这里form怎样替换,这样写会找不到form对象
}.....
<input type="button" onclick = "check(this.form)">
document.form.radio.checked = true;//这里form怎样替换,这样写会找不到form对象
}.....
<input type="button" onclick = "check(this.form)">
<input type="radio" name="radio">
</form>
<Script Language="JavaScript">
var frm = "form1"
document.forms[frm].radio.checked = true
</script>
document.forms[form].radio.checked = true;