内置对象

JavaScript 中有很多内置对象，它们可以直接在 TypeScript 中当做定义好了的类型。

ECMAScript 的内置对象

Boolean、Number、string、RegExp、Date、Error

let b: Boolean = new Boolean(1);
console.log(b);
let n: Number = new Number(true);
console.log(n);
let s: String = new String('哔哩哔哩关注小满zs');
console.log(s);
let d: Date = new Date();
console.log(d);
let r: RegExp = /^1/;
console.log(r);
let e: Error = new Error('error!');
console.log(e);

DOM 和 BOM 的内置对象

Document、HTMLElement、Event、NodeList 等

let body: HTMLElement = document.body;
let allDiv: NodeList = document.querySelectorAll('div');
//读取div 这种需要类型断言 或者加个判断应为读不到返回null
let div: HTMLElement = document.querySelector('div') as HTMLDivElement;
document.addEventListener('click', function (e: MouseEvent) {});
//dom元素的映射表
interface HTMLElementTagNameMap {
  a: HTMLAnchorElement;
  abbr: HTMLElement;
  address: HTMLElement;
  applet: HTMLAppletElement;
  area: HTMLAreaElement;
  article: HTMLElement;
  aside: HTMLElement;
  audio: HTMLAudioElement;
  b: HTMLElement;
  base: HTMLBaseElement;
  bdi: HTMLElement;
  bdo: HTMLElement;
  blockquote: HTMLQuoteElement;
  body: HTMLBodyElement;
  br: HTMLBRElement;
  button: HTMLButtonElement;
  canvas: HTMLCanvasElement;
  caption: HTMLTableCaptionElement;
  cite: HTMLElement;
  code: HTMLElement;
  col: HTMLTableColElement;
  colgroup: HTMLTableColElement;
  data: HTMLDataElement;
  datalist: HTMLDataListElement;
  dd: HTMLElement;
  del: HTMLModElement;
  details: HTMLDetailsElement;
  dfn: HTMLElement;
  dialog: HTMLDialogElement;
  dir: HTMLDirectoryElement;
  div: HTMLDivElement;
  dl: HTMLDListElement;
  dt: HTMLElement;
  em: HTMLElement;
  embed: HTMLEmbedElement;
  fieldset: HTMLFieldSetElement;
  figcaption: HTMLElement;
  figure: HTMLElement;
  font: HTMLFontElement;
  footer: HTMLElement;
  form: HTMLFormElement;
  frame: HTMLFrameElement;
  frameset: HTMLFrameSetElement;
  h1: HTMLHeadingElement;
  h2: HTMLHeadingElement;
  h3: HTMLHeadingElement;
  h4: HTMLHeadingElement;
  h5: HTMLHeadingElement;
  h6: HTMLHeadingElement;
  head: HTMLHeadElement;
  header: HTMLElement;
  hgroup: HTMLElement;
  hr: HTMLHRElement;
  html: HTMLHtmlElement;
  i: HTMLElement;
  iframe: HTMLIFrameElement;
  img: HTMLImageElement;
  input: HTMLInputElement;
  ins: HTMLModElement;
  kbd: HTMLElement;
  label: HTMLLabelElement;
  legend: HTMLLegendElement;
  li: HTMLLIElement;
  link: HTMLLinkElement;
  main: HTMLElement;
  map: HTMLMapElement;
  mark: HTMLElement;
  marquee: HTMLMarqueeElement;
  menu: HTMLMenuElement;
  meta: HTMLMetaElement;
  meter: HTMLMeterElement;
  nav: HTMLElement;
  noscript: HTMLElement;
  object: HTMLObjectElement;
  ol: HTMLOListElement;
  optgroup: HTMLOptGroupElement;
  option: HTMLOptionElement;
  output: HTMLOutputElement;
  p: HTMLParagraphElement;
  param: HTMLParamElement;
  picture: HTMLPictureElement;
  pre: HTMLPreElement;
  progress: HTMLProgressElement;
  q: HTMLQuoteElement;
  rp: HTMLElement;
  rt: HTMLElement;
  ruby: HTMLElement;
  s: HTMLElement;
  samp: HTMLElement;
  script: HTMLScriptElement;
  section: HTMLElement;
  select: HTMLSelectElement;
  slot: HTMLSlotElement;
  small: HTMLElement;
  source: HTMLSourceElement;
  span: HTMLSpanElement;
  strong: HTMLElement;
  style: HTMLStyleElement;
  sub: HTMLElement;
  summary: HTMLElement;
  sup: HTMLElement;
  table: HTMLTableElement;
  tbody: HTMLTableSectionElement;
  td: HTMLTableDataCellElement;
  template: HTMLTemplateElement;
  textarea: HTMLTextAreaElement;
  tfoot: HTMLTableSectionElement;
  th: HTMLTableHeaderCellElement;
  thead: HTMLTableSectionElement;
  time: HTMLTimeElement;
  title: HTMLTitleElement;
  tr: HTMLTableRowElement;
  track: HTMLTrackElement;
  u: HTMLElement;
  ul: HTMLUListElement;
  var: HTMLElement;
  video: HTMLVideoElement;
  wbr: HTMLElement;
}

定义 Promise

如果我们不指定返回的类型 TS 是推断不出来返回的是什么类型

指定返回的类型

函数定义返回 promise 语法规则:Promise< T> 类型

function promise(): Promise<number> {
  return new Promise<number>((resolve, reject) => {
    resolve(1);
  });
}

promise().then(res => {
  console.log(res);
});