Example: {
  xml: "<input id='input' value='text'/>",
  fun: function (sys, items, opts) {
    console.log(typeof this.prop("value")); // string
  }
}

Index: {
  xml: "<div id='index'>\
       <TextBox id='foo'/>\
       <TextBox id='bar' format='int'/>\
     </div>",
  fun: function (sys, items, opts) {
    items.foo.value = "hello, world";
    items.bar.value = 27.1828;
    console.log("foo", items.foo.value);
    console.log("bar", items.bar.value);
  }
}

TextBox: {
  xml: "<input id='input' type='text'/>",
  opt: { format: "string" },
  fun: function (sys, items, opts) {
    var parse = {"int": parseInt, "float": parseFloat, "string": String}[opts.format];
    function getValue() {
      // 这里需要获取 input 的值并根据 opts.format 值选择适当的格式化函数，
    }
    function setValue(value) {
      // 这里需要根据 opts.format 值选择适当的格式化函数，对 value 进行格式化后同去赋值
    }
    return Object.defineProperty({}, "value", { get: getValue, set: setValue });
  }
}

TextBox: {
  xml: "<input id='input' type='text'/>",
  opt: { format: 'string' },
  map: { attrs: { input: "disabled value placeholder readonly" } },
  fun: function (sys, items, opts) {
    var parse = {"int": parseInt, "float": parseFloat, "string": String}[opts.format];
    function getValue() {
      return parse(sys.input.prop("value"));
    }
    function setValue(value) {
      sys.input.prop("value", parse(value));
    }
    return Object.defineProperty({}, "value", { get: getValue, set: setValue });
  }
}