类型标注@type
/** @type { any } */
const anyType = []
// 解构类型
/** @type { [string, number] } */
const [first, second] = anyType
// 对象解构同理
/** @type { { a: string, b: number } } */
const { a, b } = any
泛型@template
/**
* @template { Record<keyof any, any> } T
* @template { keyof T } K
* @param { T } obj
* @param { K } key
* @returns { T[K] } value
*/
function getVal(obj, key) {
return obj[key]
}
或者直接用TypeScript写
/**
* @type { <T extends Record<keyof any, any>, K extends keyof T>(obj: T, key: K) => T[K] }
*/
泛型参数默认值
/**
* @template { Element } [T = Element]
* @typedef { T | () => T } Getter
*/
// 相当于
type Getter<T extends Element = Element> = T | () => T
类型断言T as U
使用括号包裹要改变类型的变量，在前面用@type
const a = 12
const b = /**@type {string}*/(/**@type {unknown}*/(a))
const b = a as unknown as string
// as const
const c = /**@type { const }*/([1, 2, 3])
const c = [1, 2, 3] as const
函数重载
使用TypeScript写
/**
* @type {{
* (a: any) => any;
* (a: any, b: any) => any;
* }}
*/
function someFn() {/***/}
或者手动判断
/**
* @template { Record<keyof any, any> } T
* @template { keyof T | (keyof T)[] } K
* @param { T } obj
* @param { K } key
* @return { K extends any[] ? T : T[K] }
*/
