访问潜在空/未定义变量的属性- javascript

var obj = null;
console.log(obj.property); // TypeError: Cannot read property 'property' of null

var obj2;
console.log(obj2.property); // TypeError: Cannot read property 'property' of undefined

var obj = null;
if (obj !== null && typeof obj.property !== 'undefined') {
  console.log(obj.property);
} else {
  console.log('obj.property is undefined or null');
}

var obj2;
if (typeof obj2 !== 'undefined' && obj2 !== null && typeof obj2.property !== 'undefined') {
  console.log(obj2.property);
} else {
  console.log('obj2.property is undefined or null');
}

var obj = null;
console.log(obj?.property); // undefined

var obj2;
console.log(obj2?.property); // undefined