var arr = [
  { name: 'John', age: 25 },
  { name: 'Amy', age: 30 },
  { name: 'Tom', age: 20 }
];

console.log(arr[0].name); // 输出 "John"
console.log(arr[1].age);  // 输出 30

var arr = [
  ['John', 25],
  ['Amy', 30],
  ['Tom', 20]
];

console.log(arr[0][0]); // 输出 "John"
console.log(arr[1][1]); // 输出 30

function Person(name, age) {
  this.name = name;
  this.age = age;
}

Person.prototype.getDetails = function() {
  return 'Name: ' + this.name + ', Age: ' + this.age;
};

var arr = [
  new Person('John', 25),
  new Person('Amy', 30),
  new Person('Tom', 20)
];

console.log(arr[0].getDetails()); // 输出 "Name: John, Age: 25"
console.log(arr[1].name);         // 输出 "Amy"