入力禁则文字check

hdnProhibit：后台设定的禁止入力文字。

function ProhibitCheck(Item) {
    var sw;
    var i;
    var j;
    var cnst;
    var ret;

    ret = "";

    try {
        cnst = document.forms[0].hdnProhibit.value;
    }
    catch (e) {
        cnst = "";
    }

    if (cnst != "") {
        for (i = 0; i < Item.length; i++) {

            sw = "ok";
            for (j = 0; j < cnst.length; j++) {
                if (cnst.charAt(j) == (Item.charAt(i))) {
                    sw = "ng";
                }
            }

            if (sw == "ng") {
                ret = ret + Item.charAt(i);
            }
        }
    }

    return ret;
}