text: 
  class MyClass {
    constructor (data) {
      this.data = {
        'a': 1,
        'b': 2
      }
    }
  }
  
  let handler = {
    get: function (target, name) {
      if (name in target.data) {
        return target.data[name]
      } else {
        return 37
      }
    }
  }
  
  let instance = new MyClass()
  
  let c = new Proxy(instance, handler)
  
  console.log(c.a)
  console.log(c.b)
  console.log(c.c)
  