TypeScript 4.1 正式 GA

TypeScript 4.1 已正式发布。

使用以下命令通过 npm 获取：

npm install -D typescript

新版本带来了不少新功能：新的检查标志、提升编辑器效率和速度。

function setVerticalAlignment(pos: "top" | "middle" | "bottom") {// ...}setVerticalAlignment("middel");//                   ~~~~~~~~// error: Argument of type '"middel"' is not assignable to//        parameter of type '"top" | "middle" | "bottom"'.

type Options = {
[K in "noImplicitAny" | "strictNullChecks" | "strictFunctionTypes"]?: boolean
};// same as//   type Options = {//       noImplicitAny?: boolean,//       strictNullChecks?: boolean,//       strictFunctionTypes?: boolean//   };

type ElementType<T> =
T extends ReadonlyArray<infer U> ? ElementType<U> : T;function deepFlatten<T extends readonly unknown[]>(x: T): ElementType<T>[] {
throw "not implemented";
}
// All of these return the type 'number[]':
deepFlatten([1, 2, 3]);
deepFlatten([[1], [2, 3]]);
deepFlatten([[1], [[2]], [[[3]]]]);

interface Options {
path: string;
permissions: number;// Extra properties are caught by this index signature.[propName: string]: string | number;
}function checkOptions(opts: Options) {
opts.path // stringopts.permissions // number// These are all allowed too!// They have the type 'string | number'.opts.yadda.toString();
opts["foo bar baz"].toString();
opts[Math.random()].toString();
}

// @filename: first.tsexport class C { }// @filename: main.tsimport * as first from './first';/**
 * @see first.C
 */function related() { }

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