using Jint;
    public class JsEvaluator
    {
        static Engine _engine;
        static JsEvaluator()
        {
            _engine = new Engine();
        }

        /// <summary>解析表达式值</summary>
        public object Eval(string expression)
        {
            var cmd = $"eval({expression.Quote()})";
            return _engine.Execute(cmd).GetCompletionValue().ToObject();
        }

        /// <summary>
        /// 转化为日期时间必须用这个函数。格式如：new Date('2018/01/01 12:00:00')
        /// </summary>
        public DateTime EvalDateTime(string expression)
        {
            var cmd = $"eval({expression.Quote()}).toLocaleString()";
            var o = _engine.Execute(cmd).GetCompletionValue().ToObject();
            return Convert.ToDateTime(o);
        }
    }

var eval = new JsEvaluator();
var b = eval.Eval("5 > 4");
var d = eval.Eval("2.5");
var o = eval.Eval("new Date()");
var t = eval.EvalDateTime("new Date('2018/01/01 12:00:00')");