typescript 中常见的公用方法封装：

hasOwn：判断val是否含有属性key;

const hasOwnProperty = Object.prototype.hasOwnProperty
export const hasOwn = (
  val: object,
  key: string | symbol
): key is keyof typeof val => hasOwnProperty.call(val, key)

isArray：判断是否为数组；

export const isArray = Array.isArray

isFunction: 判断是否为函数

export const isFunction = (val: unknown): val is Function =>
  typeof val === 'function'

isString:判断是否为字符串

export const isString = (val: unknown): val is string => typeof val === 'string'

isSymbol:判断是否为symbol

export const isSymbol = (val: unknown): val is symbol => typeof val === 'symbol'

isObject:判断是否为object

export const isObject = (val: unknown): val is Record<any, any> =>
  val !== null && typeof val === 'object'

isPromise:判断是否为promise

export function isPromise<T = any>(val: unknown): val is Promise<T> {
  return isObject(val) && isFunction(val.then) && isFunction(val.catch)
}

isPlainObject:判断是否为plainObject

export const objectToString = Object.prototype.toString

export const toTypeString = (value: unknown): string =>
  objectToString.call(value)

export const isPlainObject = (val: unknown): val is object =>
  toTypeString(val) === '[object Object]'

vue-next(vue3)中常见的类型判断方法封装

typescript 中常见的公用方法封装：