数据类型判断

使用 toString() 检测对象类型

• 可以通过 toString() 来获取每个对象的类型。为了每个对象都能通过 Object.prototype.toString() 来检测，需要以 Function.prototype.call() 或者 Function.prototype.apply() 的形式来调用。

const toString = Object.prototype.toString

toString.call(new Date); // [object Date]
toString.call(undefined); // [object Undefined]

定义is方法

function is(val: unknown, type: string) {
  return toString.call(val) === `[object ${type}]`
}

判断是否为String

function isString(val: unknown): val is string {
  return is(val, 'String')
}

判断是否为Number

export function isNumber(val: unknown): val is number {
  return is(val, 'Number')
}

判断是否为Boolean

function isBoolean(val: unknown): val is boolean {
  return is(val, 'Boolean')
}

判断是否undefined

function isUndefined<T = unknown>(val?: T): val is T {
  return typeof val === 'undefined'
}

判断是null

function isNull(val: unknown): val is null {
  return val === null
}

判断是否为Object

function isObject(val: any): val is Record<any, any> {
  return val !== null && is(val, 'Object')
}

判断是否为function

function isFunction(val: unknown): val is Function {
  return typeof val === 'function'
}

判断是否为Array

function isArray(val: any): val is Array<any> {
  return val && Array.isArray(val)
}

判断是否为Date

function isDate(val: unknown): val is Date {
  return is(val, 'Date')
}

判断是否为RegExp

function isRegExp(val: unknown): val is RegExp {
  return is(val, 'RegExp')
}

判断是否为Map

function isMap(val: unknown): val is Map<any, any> {
  return is(val, 'Map')
}

判断是否为Promise

function isPromise<T = any>(val: any): val is Promise<T> {
  return is(val, 'Promise') && isFunction(val.then) && isFunction(val.catch)
}

判断是否为JSON

function isJsonObjectString(val: string): val is string {
  if (!val) {
    return false
  }
  return val.startsWith('{') && val.endsWith('}')
}

判断是否为Window

function isWindow(val: any): val is Window {
  return typeof window !== 'undefined' && is(val, 'Window')
}

判断是否为Element

function isElement(val: unknown): val is Element {
  return isObject(val) && !!val.tagName
}

判断是否为Url

function isUrl(path: string): boolean {
  const reg =
    /(((^https?:(?://)?)(?:[-;:&=+$,\w]+@)?[A-Za-z0-9.-]+(?::\d+)?|(?:www.|[-;:&=+$,\w]+@)[A-Za-z0-9.-]+)((?:/[+~%/.\w-_]*)???(?:[-+=&;%@.\w_]*)#?(?:[\w]*))?)$/
  return reg.test(path)
}

判断是否为空

function isEmpty<T = unknown>(val: T): val is T {
  if (isArray(val) || isString(val)) {
    return val.length === 0
  }

  if (val instanceof Map || val instanceof Set) {
    return val.size === 0
  }

  if (isObject(val)) {
    return Object.keys(val).length === 0
  }

  return false
}