Vue3 中 那些使用的工具函数

babelParserDefaultPlugins

export const babelParserDefaultPlugins = [
  'bigInt',
  'optionalChaining',
  'nullishCoalescingOperator'
] as const

EMPTY_OBJ 空对象

export const EMPTY_OBJ: { readonly [key: string]: any } = __DEV__
  ? Object.freeze({})
  : {}

EMPTY_ARR 空数组

export const EMPTY_ARR = __DEV__ ? Object.freeze([]) : []

NOOP 空函数

export const NOOP = () => {}

NO 永远返回 false 的函数

/**
 * Always return false.
 */
export const NO = () => false

isOn 判断字符串是不是 on 开头

const onRE = /^on[^a-z]/
export const isOn = (key: string) => onRE.test(key)

isModelListener

export const isModelListener = (key: string) => key.startsWith('onUpdate:')

extend 继承

export const extend = Object.assign

remove 移除数组的一项

export const remove = <T>(arr: T[], el: T) => {
  const i = arr.indexOf(el)
  if (i > -1) {
    arr.splice(i, 1)
  }
}

hasOwn 是不是自己本身所拥有的属性

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

isArray 判断数组

export const isArray = Array.isArray

isMap 判断是不是 Map 对象

export const isMap = (val: unknown): val is Map<any, any> =>
  toTypeString(val) === '[object Map]'

isSet 判断是不是 Set 对象

export const isSet = (val: unknown): val is Set<any> =>
  toTypeString(val) === '[object Set]'

isDate 判断是不是 Date 对象

export const isDate = (val: unknown): val is Date => val instanceof Date

isFunction 判断是不是函数

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

isString 判断是不是字符串

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

isSymbol 判断是不是 Symbol

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

isObject 判断是不是对象

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

isPromise 判断是不是 Promise

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

objectToString 对象转字符串

export const objectToString = Object.prototype.toString

toTypeString 对象转字符串

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

toRawType 对象转字符串 截取后几位

export const toRawType = (value: unknown): string => {
  // extract "RawType" from strings like "[object RawType]"
  return toTypeString(value).slice(8, -1)
}

isPlainObject 判断是不是纯粹的对象

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

isIntegerKey 判断是不是

export const isIntegerKey = (key: unknown) =>
  isString(key) &&
  key !== 'NaN' &&
  key[0] !== '-' &&
  '' + parseInt(key, 10) === key

isReservedProp

export const isReservedProp = /*#__PURE__*/ makeMap(
  // the leading comma is intentional so empty string "" is also included
  ',key,ref,' +
    'onVnodeBeforeMount,onVnodeMounted,' +
    'onVnodeBeforeUpdate,onVnodeUpdated,' +
    'onVnodeBeforeUnmount,onVnodeUnmounted'
)

cacheStringFunction 缓存

const cacheStringFunction = <T extends (str: string) => string>(fn: T): T => {
  const cache: Record<string, string> = Object.create(null)
  return ((str: string) => {
    const hit = cache[str]
    return hit || (cache[str] = fn(str))
  }) as any
}

const camelizeRE = /-(\w)/g
/**
 * @private
 */
export const camelize = cacheStringFunction(
  (str: string): string => {
    return str.replace(camelizeRE, (_, c) => (c ? c.toUpperCase() : ''))
  }
)

const hyphenateRE = /\B([A-Z])/g
/**
 * @private
 */
export const hyphenate = cacheStringFunction((str: string) =>
  str.replace(hyphenateRE, '-$1').toLowerCase()
)

/**
 * @private
 */
export const capitalize = cacheStringFunction(
  (str: string) => str.charAt(0).toUpperCase() + str.slice(1)
)

/**
 * @private
 */
export const toHandlerKey = cacheStringFunction(
  (str: string) => (str ? `on${capitalize(str)}` : ``)
)

hasChanged 判断是不是有变化

// compare whether a value has changed, accounting for NaN.
export const hasChanged = (value: any, oldValue: any): boolean =>
  value !== oldValue && (value === value || oldValue === oldValue)

invokeArrayFns 执行数组里的函数

export const invokeArrayFns = (fns: Function[], arg?: any) => {
  for (let i = 0; i < fns.length; i++) {
    fns[i](arg)
  }
}

def 定义

export const def = (obj: object, key: string | symbol, value: any) => {
  Object.defineProperty(obj, key, {
    configurable: true,
    enumerable: false,
    value
  })
}

toNumber 转数字

export const toNumber = (val: any): any => {
  const n = parseFloat(val)
  return isNaN(n) ? val : n
}

getGlobalThis 全局对象

let _globalThis: any
export const getGlobalThis = (): any => {
  return (
    _globalThis ||
    (_globalThis =
      typeof globalThis !== 'undefined'
        ? globalThis
        : typeof self !== 'undefined'
          ? self
          : typeof window !== 'undefined'
            ? window
            : typeof global !== 'undefined'
              ? global
              : {})
  )
}