js jquery实时计算输入字符

在项目中需要倒还可以输入多少字符

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支持键盘输入，sogou,小键盘

　　　　　　//多个事件keydown keypress keyup
        $(".ujpg-box-5-textarea").bind("keydown keypress keyup", function() {

            var id = $(this).attr("id");

            var txta = $("#" + id).val();
            if (txta.length > 140) {
                var trueconten = txta.substring(0, 140)
                $("#" + id).val(trueconten);
            }

            $("#divSYZ_txtReply").html("只可输入" + (140 - txta.length) + "个文字");
        })