vue3 工具函数学习

摩洛克
116 阅读3分钟

前言

学习目标

本文分析vue-next的shared模块的工具函数

源码地址：shared/src/index.ts

源码分析

源码中 DEV 编译后是环境判断 process.env.NODE_ENV !== 'production'

babel解析默认配置

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

babel 解析默认配置,这里使用了 const 断言（as const）如果没有的话 babelParserDefaultPlugins 会被推断成 string[]

bigInt 是一种内置对象，它提供了一种方法来表示大于 2^53 - 1 的整数

optionalChaining 可选链操作符(?.)

nullishCoalescingOperator 空值合并运算符(??)

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 返回 false 的函数

export const NO = () => false

isOn 是否on开头

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

isModelListener 是否 Model 事件

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

extend 合并

export const extend = Object.assign

remove 删除数组某项

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

hasOwn 是否存在某属性

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

toTypeString 对象转换为字符串

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

isArray 是否是数组

export const isArray = Array.isArray

isMap 是否是Map

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

isSet 是否是Set

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

isDate 是否是日期

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

isFunction 是否是函数

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

isString 是否是字符串

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

isSymbol 是否是symbol

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

isObject 是否是纯对象

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

isPromise 是否是promise

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

toRawType 类型截取

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

isPlainObject 是否是纯字符串

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

isIntegerKey 是不是数字类型

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

isReservedProp 是否为保留字段

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

makeMap 根据逗号分隔的字符串生成Map映射，这里是生成vue的一些内置属性和生命周期Map映射

cacheStringFunction 函数缓存

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
}

下文的字母大小写转换使用该函数，缓存可以减少相同正则匹配等操作

camelize 连字符转驼峰

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

如：on-click => onClick

hyphenate 大写转小写

// \B 是指 非 \b 单词边界。
const hyphenateRE = /\B([A-Z])/g
export const hyphenate = cacheStringFunction((str: string) =>
  str.replace(hyphenateRE, '-$1').toLowerCase()
)

capitalize 首字母大写

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

toHandlerKey 首字母大写后前面加on

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

hasChanged 是否有变化

export const hasChanged = (value: any, oldValue: any): boolean => !Object.is(value, oldValue)

Object.is() 方法判断两个值是否为同一个值。如果满足以下条件则两个值相等

invokeArrayFns 执行函数

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

def 对象属性代理

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
        : {})
  )
}

总结

基于ts的各种工具函数封装，对于ts初学者来讲也是不错的借鉴。

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