js 判断宽松相等

/** Vue源码 296行
   * Check if two values are loosely equal - that is,
   * if they are plain objects, do they have the same shape?
   */
function isObject(data){
   return typeof data === 'object' && data !== null
}
function looseEqual(a,b){
   if(a===b) return true
   let isObjectA = isObject(a)
   let isObjectB = isObject(a)
   if(isObjectA && isObjectB){
      let isArrayA = Array.isArray(a)
      let isArrayB = Array.isArray(b)
      if(isArrayA && isArrayB){
         return isArrayA.length === isArrayB && isArray.every((i,k)=> looseEqual(i,b[k]))
      }else if(a instanceof Date && b instanceof Date){
         return a.getTime() === b.getTime()
      }else if(!isArrayA && !isArrayB){
         let keysA = Object.keys(a)
         let keysB = Object.keys(b)
         return keysA.length === keysB.length && keysA.every(i=>looseEqual(a[i],b[i])) 
      }else{
         /* istanbul ignore next */
         return false
      }
   }else if(!isObjectA && !isObjectB){
      return String(a) === String(b)
   }else{
      /* istanbul ignore next */
      return false
   }
}