通过 in 和 hasOwnproperty 检测对象上是否有某个属性

Question

var obj = {};
Object.defineProperty(obj, 'x', {
  value:7,
  writable:true,
  configurable:true,
  enumerable:true
})
obj.x = 77;
console.log(obj.x);
console.log('x' in obj);
console.log(obj.hasOwnProperty('x'));
var arr = {
  name:'jawil',
  age:23,
  sex:"man"
}