Javascript - 如何将对象中的 key.value 大写？

Question

如何将每个联系人名字的首字母大写？

 String.prototype.capitalize = function (string) { return string.charAt(0).toUpperCase() + string.slice(1);}

 var contactList = {};

 contactList.bobSmith = {
 firstName: "bob",
 lastName: "smith",
 location: "new york"
};

contactList.johnDoe = {
 firstName: "john",
 lastName: "doe",
 location: "san francisco"
};

var contact2 = contactList["johnDoe"].firstName;
contact1.capitalize();
contact2.capitalize();
console.log(contact1 + " " + contact2);

我收到一条错误消息，内容为“Uncaught TypeError: Cannot read property 'charAt' of undefined”。

Answer 1

function () { return this.charAt(0).toUpperCase() + this.slice(1);