core/packages/shared/src/index.ts

import { makeMap } from './makeMap'

export { makeMap }
export * from './patchFlags'
export * from './shapeFlags'
export * from './globalsWhitelist'
export * from './codeframe'
export * from './mockWarn'
export * from './normalizeProp'
export * from './domTagConfig'
export * from './domAttrConfig'
export * from './escapeHtml'
export * from './looseEqual'

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

export const NOOP = () => {}

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

export const isOn = (key: string) => key[0] === 'o' && key[1] === 'n'

export const extend = <T extends object, U extends object>(
  a: T,
  b: U
): T & U => {
  for (const key in b) {
    ;(a as any)[key] = b[key]
  }
  return a as any
}

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

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

export const isArray = Array.isArray
export const isFunction = (val: unknown): val is Function =>
  typeof val === 'function'
export const isString = (val: unknown): val is string => typeof val === 'string'
export const isSymbol = (val: unknown): val is symbol => typeof val === 'symbol'
export const isObject = (val: unknown): val is Record<any, any> =>
  val !== null && typeof val === 'object'

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

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

export const toRawType = (value: unknown): string => {
  return toTypeString(value).slice(8, -1)
}

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

export const isReservedProp = /*#__PURE__*/ makeMap(
  'key,ref,' +
    'onVnodeBeforeMount,onVnodeMounted,' +
    'onVnodeBeforeUpdate,onVnodeUpdated,' +
    'onVnodeBeforeUnmount,onVnodeUnmounted'
)

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
export const camelize = cacheStringFunction(
  (str: string): string => {
    return str.replace(camelizeRE, (_, c) => (c ? c.toUpperCase() : ''))
  }
)

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

export const capitalize = cacheStringFunction(
  (str: string): string => {
    return str.charAt(0).toUpperCase() + str.slice(1)
  }
)

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

// for converting {{ interpolation }} values to displayed strings.
export const toDisplayString = (val: unknown): string => {
  return val == null
    ? ''
    : isArray(val) || (isPlainObject(val) && val.toString === objectToString)
      ? JSON.stringify(val, null, 2)
      : String(val)
}