vue-draggle源码中的策略模式和柯里化

 eventsListened.forEach(elt => {
      optionsAdded["on" + elt] = delegateAndEmit.call(this, elt);
    });

const eventsListened = ["Start", "Add", "Remove", "Update", "End"];

function delegateAndEmit(evtName) {
  return evtData => {
    if (this.realList !== null) {
      this["onDrag" + evtName](evtData);
    }
    emit.call(this, evtName, evtData);
  };
}