Question

如何定义对象的属性，因此如果其中一个被更改，则所有其他属性都会自动更新。

到目前为止，我已经提出了这个代码，但它不起作用：

function CreateNamed(first, last) {
    Object.defineProperties(this, {
           "firstName": {
            value: first,
            writable: true
        },
            "lastName": {
            value: last,
            writable: true
        },
            "fullName": {
            value: first + ' ' + last,
            writable: true
        }
    });
}

因此，在创建新对象后，可以对其进行适当更改：

var b = new CreateNamed('Bill', 'Gates'); // Bill Gates
b.firstName = 'Paul'; // b.fullName = Paul Gates
b.lastName = 'Wood'; // b.fullname = Paul Wood
b.fullName = 'Chuck Norris' // b.firstName = Chuck, b.lastName = Norris

Answer 1

value不是动态计算的。随着对象的变化，它不会发生变化。为了动态计算属性，您需要使用get and set定义getter和setter：

获取
  一个函数，用作属性的getter，如果没有getter则不定义。函数返回将用作   财产的价值。默认为undefined。

设置
  用作属性的setter的函数，如果没有setter则为undefined。该功能将仅收到   参数赋予属性的新值。默认为   未定义。

＆＃13;
＆＃13;
function CreateNamed(first, last) { this.first = first; this.last = last; Object.defineProperties(this, { "firstName": { get: function() { return this.first; }, set: function(name) { this.first = name; } }, "lastName": { get: function() { return this.last; }, set: function(name) { this.last = name; } }, "fullName": { get: function () { return this.first + ' ' + this.last }, set: function (name) { if (!name.match(/^[a-z]+ [a-z]+$/)) throw new Error('I cannot parse that name') var parts = name.split(' ') this.first = parts[0]; this.last = parts[1]; } } }); } var user = new CreateNamed('bob', 'smith'); document.write(user.fullName); // bob smith user.firstName = "john"; document.write(user.fullName); // john smith user.fullName = "tony brian"; document.write(user.firstName); // tony document.write(user.lastName); // brian
＆＃13;
＆＃13;
＆＃13;

Answer 2

@meagar's answer是正确的。

但是有一种更简单的方法：只需像往常一样分配firstName和lastName属性，然后只为fullName定义一个getter和setter：

function CreateNamed(first, last) {
  this.firstName = first;
  this.lastName = last;
  Object.defineProperty(this, "fullName", {
    get: function () { return this.firstName + ' ' + this.lastName },
    set: function (name) {
      name = name.split(' ');
      if(name.length != 2) throw new Error('I cannot parse that name');
      this.firstName = name[0];
      this.lastName = name[1];
    }
  });
}

function CreateNamed(first, last) {
  this.firstName = first;
  this.lastName = last;
  Object.defineProperty(this, "fullName", {
    get: function () { return this.firstName + ' ' + this.lastName },
    set: function (name) {
      name = name.split(' ');
      if(name.length != 2) throw new Error('I cannot parse that name');
      this.firstName = name[0];
      this.lastName = name[1];
    }
  });
}

var ouput = [];

var user = new CreateNamed('bob', 'smith');
ouput.push(user.fullName); // bob smith

user.firstName = "john"; 
ouput.push(user.fullName); // john smith

user.fullName = "tony brian";
ouput.push(user.firstName); // tony
ouput.push(user.lastName); // brian

document.body.innerHTML = ouput.join('<br />');

使对象的所有属性都可变

2 个答案: