## $delete 同样，object 删除属性，自身也是无感知的，这样 vue 就无法追踪被删除的数据 ``` Vue.prototype.$delete = del ``` ``` export function del (target: Array | Object, key: any) { ... if (Array.isArray(target) && isValidArrayIndex(key)) { target.splice(key, 1) return } const ob = (target: any).__ob__ ... if (!hasOwn(target, key)) { return } delete target[key] if (!ob) { return } ob.dep.notify() } ```