// 判断是否为undefined或null

const isDef = (v) => {
  return v !== undefined && v !== null
}

// 判断是否为Promise 函数

const isPromise = (val) => {
  return (
    val !== undefine &&
    typeof val.then === 'function' &&
    typeof val.catch === 'function'
  )
}

// 判断是否为简单数据类型

const isPrimitive (value) => {
  return (
    typeof value === 'string' ||
    typeof value === 'number' ||
    typeof value === 'symbol' ||
    typeof value === 'boolean'
  )
}

// 严格检查复杂数据类型

const isPlainObject = (obj) => {
  return Object.prototype.toString.call(obj) === '[object Object]'
}

const isRegExp = (v) => {
  return Object.prototype.toString.call(v) === '[object RegExp]'
}

// 将驼峰字符串转成连接符 magicEightTall 转换成 magic-eight-tall

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

// 将连接符转成驼峰字符串 magic-eight-tall 转换成 magicEightTall

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

// 如果不想重复转换，可用以下方法调用转换函数

const cached = (fn) => {
    const cache = Object.create(null)
    console.log(cache);
    return ((str) => {
      const hit = cache[str]
      return hit || (cache[str] = fn(str))
    })
};

// 例
const camelize = cached((str) => {
    return str.replace(camelizeRE, (_, c) => c ? c.toUpperCase() : '')
})

链接: https://www.fly63.com/article/detial/5531