Function createEventProp

src/app/service/content/create_context.ts:309–350

(key: string)

  // 用 eventHandling 机制模拟 onxxxxxxx 事件设置
  // 监听事件实际上的方法是eventObject.handleEvent
  const createEventProp = (key: string) => {
    const eventName = (<string>key).slice(2);
    // 赋值变量
    const eventObject: EventListenerObject & { fn: any } = {
      fn: null,
      handleEvent(event) {
        const fn = mySandbox[key];
        if (!fn || fn !== this.fn) {
          global.removeEventListener(eventName, eventObject);
          this.fn = null;
        } else {
          fn.call(mySandbox, event);
        }
      },
    };
    return {
      get() {
        return eventObject.fn;
      },
      set(newVal: EventListener | any) {
        const { fn } = eventObject;
        if (newVal !== fn) {
          if (isPrimitive(newVal)) {
            // 按照实际操作，primitive types (number, string, boolean, ...) 会被转换成 null
            newVal = null;
          }
          if (typeof fn !== typeof newVal) {
            // function <-> function 时无需重新监听
            if (typeof fn === "function") {
              // 停止当前事件监听
              global.removeEventListener(eventName, eventObject);
            } else if (typeof newVal === "function") {
              // 非primitive types 的话，只考虑 function type
              // Symbol, Object (包括 EventListenerObject ) 等只会保存而不进行事件监听
              global.addEventListener(eventName, eventObject);
            }
          }
          eventObject.fn = newVal;
        }
      },
    };
  };

  for (const key of Object.keys(eventDescs)) {
    const eventSetterGetter = createEventProp(key);