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)
})
当你在使用一些常用的方法的时候，TypeScript 实际上已经帮你做了很多类型判断的工作了
而他们的定义文件，则在 TypeScript 核心库的定义文件中
代码雨案例
let canvas = document.querySelector('#canvas') as HTMLCanvasElement
let ctx = canvas.getContext('2d') as CanvasRenderingContext2D
canvas.height = screen.availHeight; //可视区域的高度
canvas.width = screen.availWidth; //可视区域的宽度
let str: string[] = 'XMZSWSSBXMZSWSSBXMZSWSSBXMZSWSSBXMZSWSSB'.split('')
let Arr = Array(Math.ceil(canvas.width / 10)).fill(0) //获取宽度例如1920 / 10 192
console.log(Arr);
const rain = () => {
ctx.fillStyle = 'rgba(0,0,0,0.05)'//填充背景颜色
ctx.fillRect(0, 0, canvas.width, canvas.height)//背景
ctx.fillStyle = "#0f0"; //文字颜色
Arr.forEach((item, index) => {
ctx.fillText(str[ Math.floor(Math.random() * str.length) ], index * 10, item + 10)
Arr[index] = item >= canvas.height || item > 10000 * Math.random() ? 0 : item + 10; //添加随机数让字符随机出现不至于那么平整
})
console.log(Arr);
}
setInterval(rain, 40)
