连续点击ajax 防止多次提交

    var isAjax=false;
    $('#count_down').click(function(){


        if(isAjax){
            return;
        }
        isAjax=true;
        var _phone = $('#phone_number').val();

        if(_phone == ''){
            isAjax=false;
            alert('手机号不能为空');return;
        }else if(_phone.length !== 11){
            isAjax=false;
            alert('请输入正确位数手机号');return;
        }

        $.ajax({
            type:'post',
            url:"{:U('Login/send_sms')}",
            data:{phone:_phone,type:1},
            success:function(data){
                if(data.status == 'ok'){
                    alert(data.content);return
                    isAjax=false;
                }else{
                    isAjax=false;
                    alert(data.content);return
                }
            }
        });
    });