如何访问聚合物元素模板内js文件中定义的函数?

有什么方法可以访问HTML元素中的函数吗?

Polymer的数据绑定系统设计用于将值绑定到模板。这些值通常只是文字(例如字符串和数字)或普通ole javascript对象,例如。 {a: 'someval', b: 5} 聚合物的数据绑定系统是 不 设计用于将函数绑定到模板,您不能仅在模板内使用javascript。 (If you're really into that idea, check out React as a replacement to polymer) .

computed property 。创建一个对其他变量的更改做出反应的计算属性,而不是在模板内调用函数。当特性的状态更改时,计算的特性也将更改。这种状态可以被视为函数的参数。

<link rel="import" href="https://polygit.org/components/polymer/polymer-element.html">
<link rel="import" href="custom-js-import.html">

<dom-module id="custom-element">

  <template>
    <div>
      Hello
    </div>
    <label>
      <input type="number" value="{{flag::input}}">
    </label>
    <h1>from flag: [[flag]]</h1>
    <div id="data"></div>
    <div>{{boundComputedData}}</div><!-- Unable to access this from here -->
    <div>{{getLocalData()}}</div>
  </template>

  <script>
    // Define the class for a new element called custom-element
    class CustomElement extends Polymer.Element {
      static get is() {
        return "custom-element";
      }
      constructor() {
        super();
      }

      getData(flag) {
        const flagAsNumber = parseInt(flag);
        if (flagAsNumber === 1) {
          return "one";
        } else {
          return "not one";
        }
      }

      ready() {
        super.ready();
        this.$.data.textContent = "I'm a custom-element.";
        console.log(this.getData(1)); //can be easily accessed from here
      }

      getLocalData() {
        return "local";
      }



      static get properties() {
        return {
          flag: {
            type: Number,
            value: 0
          },
          boundComputedData: {
            type: String,
            computed: 'getData(flag)'
          }
        };
      }

    }
    // Register the new element with the browser
    customElements.define(CustomElement.is, CustomElement);
  </script>
</dom-module>

<custom-element></custom-element>

所以我在这里做的是:

boundComputedData 并设置 computed 属性到 'getData(flag)' getData .

现在只要州政府 flag 更改时,计算属性将更新。

Rico Kahler 建议我使用 mixin .使用 解决了我的问题。您可以查看完整的工作示例 here .

<!--custom-mixin.html-->
<script>
  const CustomMixin = superclass => class extends superclass {

static get properties() {
  return {};
}

connectedCallback() {
  super.connectedCallback();
}

getData(flag) {
   if (flag === 1) {
    return "one(From Mixin)";
   } else {
    return "not one(From Mixin)";
   }
  }
 };
</script>

记住导入mixin文件并将该mixin添加到元素中。

<!-- custom-element.html -->
<link rel="import" href="https://polygit.org/components/polymer/polymer-element.html">
<link rel="import" href="custom-mixin.html">

<dom-module id="custom-element">

  <template>
    <div>
      Hello
    </div>
    <div id="data"></div>
    <div>{{getData(1)}}</div>
    <!-- Unable to access this from here -->
    <div>{{getLocalData()}}</div>
  </template>

  <script>
    // Define the class for a new element called custom-element
    class CustomElement extends CustomMixin(Polymer.Element) {
        static get is() {
          return "custom-element";
        }
        constructor() {
          super();
        }

        ready() {
          super.ready();
          this.$.data.textContent = "I'm a custom-element.";
          console.log(getData(1)); //can be easily accessed from here
        }

        getLocalData() {
          return "local";
        }

      }
      // Register the new element with the browser
    customElements.define(CustomElement.is, CustomElement);
  </script>
</dom-module>