相关疑难解决方法(0)

根据这篇文章，当在 TypeScript 中启用严格的空值检查时，除非联合明确允许，否则您不能分配null或分配undefined给变量。

// required value
let req: string;
req = "Something";  // OK
req = null;      // Error
req = undefined; // Error

// nullable value
let nbl: string | null;
nbl = "Something";  // OK
nbl = null;      // OK
nbl = undefined; // Error

但是在 TypeScript 中null允许在可选值中使用吗？

// optional value
let opt?: string; // (actually invalid, as optional types cannot be used for variable declarations, but that's …

美好的一天.我是使用VSCode的Type Script的新手.

获得以下错误:

error TS2345: Argument of type 'Menu' is not assignable to parameter of type '{ state: string; name: string; type: string; icon: string;
 badge?: undefined; children?: undefine...'

该代码:

import { Injectable } from '@angular/core';

export interface BadgeItem {
  type: string;
  value: string;
}

export interface ChildrenItems {
  state: string;
  name: string;
  type?: string;
}

export interface Menu {
  state: string;
  name: string;
  type: string;
  icon: string;
  badge?: BadgeItem[];
  children?: ChildrenItems[];
}

const MENUITEMS = …