Function mergeVNodeHook

m3u8/vue.js:2235–2266

(def, hookKey, hook)

  /*  */

  function mergeVNodeHook (def, hookKey, hook) {
    if (def instanceof VNode) {
      def = def.data.hook || (def.data.hook = {});
    }
    var invoker;
    var oldHook = def[hookKey];

    function wrappedHook () {
      hook.apply(this, arguments);
      // important: remove merged hook to ensure it's called only once
      // and prevent memory leak
      remove(invoker.fns, wrappedHook);
    }

    if (isUndef(oldHook)) {
      // no existing hook
      invoker = createFnInvoker([wrappedHook]);
    } else {
      /* istanbul ignore if */
      if (isDef(oldHook.fns) && isTrue(oldHook.merged)) {
        // already a merged invoker
        invoker = oldHook;
        invoker.fns.push(wrappedHook);
      } else {
        // existing plain hook
        invoker = createFnInvoker([oldHook, wrappedHook]);
      }
    }

    invoker.merged = true;
    def[hookKey] = invoker;
  }

  /*  */