text: /* @flow */
  
  /**
   * unicode letters used for parsing html tags, component names and property paths.
   * using https://www.w3.org/TR/html53/semantics-scripting.html#potentialcustomelementname
   * skipping \u10000-\uEFFFF due to it freezing up PhantomJS
   */
  export const unicodeRegExp = /a-zA-Z\u00B7\u00C0-\u00D6\u00D8-\u00F6\u00F8-\u037D\u037F-\u1FFF\u200C-\u200D\u203F-\u2040\u2070-\u218F\u2C00-\u2FEF\u3001-\uD7FF\uF900-\uFDCF\uFDF0-\uFFFD/
  
  /**
   * Check if a string starts with $ or _
   */
  export function isReserved (str: string): boolean {
    const c = (str + '').charCodeAt(0)
    return c === 0x24 || c === 0x5F
  }
  
  /**
   * Define a property.
   */
  // 为对象配置属性
  export function def (obj: Object, key: string, val: any, enumerable?: boolean) {
    Object.defineProperty(obj, key, {
      value: val,
      enumerable: !!enumerable,
      writable: true,
      configurable: true
    })
  }
  
  /**
   * Parse simple path.
   */
  const bailRE = new RegExp(`[^${unicodeRegExp.source}.$_\\d]`)
  export function parsePath (path: string): any {
    if (bailRE.test(path)) {
      return
    }
    const segments = path.split('.')
    return function (obj) {
      for (let i = 0; i < segments.length; i++) {
        if (!obj) return
        obj = obj[segments[i]]
      }
      return obj
    }
  }
  