当我调用数组中对象的属性时出现错误

在打字稿代码中，我有一个包含对象的数组。当我调用“getUsers(users)”函数时，它会根据需要返回结果，但在控制台中我收到此错误 “未捕获类型错误：无法读取未定义的属性“firstName” 在 getUsers (index.js:20) 在index.js：23”

let users = [
{
    firstName: "John",
    lastName: "Doe",
    age: 34
},
{
    firstName: "Jack",
    lastName: "Jackson",
    age: 23
},
{
    firstName: "Ann",
    lastName: "Watson",
    age: 24
}
];
function getUsers(users) {
for (var i = 0; i <= users.length; i++) {
    console.log(users[i].firstName + " is " + users[i].age + " years old!");
}
}
getUsers(users);

问题在于i <= users.length，它需要是i < users.length.i++会将 i 的值增加 1，但长度为 3 并且索引从 0 开始，因此元素被占用直到第二个索引，因此i <= users.length实际上会尝试访问第三个索引中未定义的元素

let users = [{
    firstName: "John",
    lastName: "Doe",
    age: 34
  },
  {
    firstName: "Jack",
    lastName: "Jackson",
    age: 23
  },
  {
    firstName: "Ann",
    lastName: "Watson",
    age: 24
  }
];

function getUsers(users) {
  for (var i = 0; i < users.length; i++) {
    console.log(users[i].firstName + " is " + users[i].age + " years old!");
  }
}
getUsers(users);