一些框架源码中的代码

const keyCodes = {
  esc: 27,
  tab: 9,
  enter: 13,
  space: 32,
  up: 38,
  left: 37,
  right: 39,
  down: 40,
  'delete': [8, 46]
}


const decodingMap = {
  '<': '<',
  '>': '>',
  '"': '"',
  '&': '&',
  '
': '\n'
}



export const hasProto = '__proto__' in {}

// Browser environment sniffing
export const inBrowser = typeof window !== 'undefined'
export const UA = inBrowser && window.navigator.userAgent.toLowerCase()
export const isIE = UA && /msie|trident/.test(UA)
export const isIE9 = UA && UA.indexOf('msie 9.0') > 0
export const isEdge = UA && UA.indexOf('edge/') > 0
export const isAndroid = UA && UA.indexOf('android') > 0
export const isIOS = UA && /iphone|ipad|ipod|ios/.test(UA)
export const isChrome = UA && /chrome\/\d+/.test(UA) && !isEdge