IT资讯 TypeScript 5.1 正式发布

caspar · 2023-06-02 21:30:08 · 热度: 9

重要变化

更智能地检查未定义返回值的函数 (undefined-Returning Functions)

旧代码

function foo() {
    // no return
}

// x = undefined
let x = foo();

//  fine - we inferred that 'f1' returns 'void'
function f1() {
    // no returns
}

//  fine - 'void' doesn't need a return statement
function f2(): void {
    // no returns
}

//  fine - 'any' doesn't need a return statement
function f3(): any {
    // no returns
}

//  error!
// A function whose declared type is neither 'void' nor 'any' must return a value.
function f4(): undefined {
    // no returns
}

新代码

//  Works in TypeScript 5.1!
function f4(): undefined {
    // no returns
}

//  Works in TypeScript 5.1!
takesFunction((): undefined => {
    // no returns
});

//  Works in TypeScript 5.1!
takesFunction(function f() {
    //                 ^ return type is undefined

    // no returns
});

//  Works in TypeScript 5.1!
takesFunction(function f() {
    //                 ^ return type is undefined

    return;
});

Getters 和 Setters 类型之间无限制

TypeScript 5.1 移除了 Get 访问器的返回类型必须可分配给其 Set 访问器类型这一限制。

携带命名空间的 JSX 标签

使用 JSX 时，TypeScript 现在支持命名空间属性名称。

import * as React from "react";

// Both of these are equivalent:
const x = <Foo a:b="hello" />;
const y = <Foo a : b="hello" />;

interface FooProps {
    "a:b": string;
}

function Foo(props: FooProps) {
    return <div>{props["a:b"]}</div>;
}

// In some library's code or in an augmentation of that library:
namespace JSX {
    interface IntrinsicElements {
        ["a:b"]: { prop: string };
    }
}

// In our code:
let x = <a:b prop="hello!" />;