Question

是否可以通过某种方式动态地组成字符串？我已经读过一些关于值传递和引用传递的信息，因此我将所有字符串创建为对象。

示例：

var foo = {str: 'foo'};
var bar = {str: foo.str + 'bar'};
var baz = {str: bar.str + 'baz'};
foo.str = 'fuu';
console.log(baz.str); //expected 'fuubarbaz', got 'foobarbaz

谢谢！

Answer 1

不，当您像这样静态定义事物时，他们将在调用该变量时使用该变量。您可以使用getters来做类似的事情：

let foo = {str: 'foo'};
let bar = {get str() { return foo.str + 'bar'; }};
let baz = {get str() { return bar.str + 'baz'; }};
foo.str = 'fuu';
console.log(baz.str); // properly outputs `fuubarbaz`

之所以有效，是吸气剂的魔力；而不是静态定义属性，而是定义一个在尝试访问属性时调用的函数。通过这种方式，它可以“响应”任何下游更改，因为它始终是动态生成的。

Answer 2

它不能像这样工作，串联foo.str +仅执行一次，加号不是被多次调用的函数。

一种执行所需操作的方法是创建一个具有3个字符串和一个方法的对象！：

const obj = {
    a: 'foo',
    b: 'bar',
    c: 'baz',
    show: function() {
        return this.a + this.b + this.c;
    }
};

console.log(obj.show());
obj.a = 'fuu';

console.log(obj.show());

Answer 3

基于puddi的回答，我想到了这一点：

console.clear()
var foo = {
  // _str is the storage of str
  _str: 'foo',
  // getter of str, always called when accessing str in a read context
  get str() {return this._str}, 
  // setter of str, always called when accessing str in a write context
  set str(str) {this._str = str}
};
// read context, so get str() of foo is called
console.log(foo.str) // "foo"

var bar = {
  // define getter function of bar, calls getter function of foo
  get str() {return foo.str + 'bar'}
};
// read context, so get str() of bar is called
console.log(bar.str) // "foobar"

var baz = {
  // define getter function of baz, calls getter function of baz
  get str() {return bar.str + 'baz'}
};
// read context, so get str() of baz is called
console.log(baz.str) // "foobarbaz"

// write context, so set str(str) of foo is called.  foo._str is now 'fuu', was 'foo'
foo.str = 'fuu';

// read context, getter of baz is called which calls getter of bar which calls getter of foo which returns _str which has the value of 'fuu'
console.log(baz.str); // "fuubarbaz"

或者，您可以使用Object.defineProperty：

console.clear();

var foo = Object.defineProperty({}, 'str', {
  enumerable: true,
  get: () => this._property_str, 
  set: (str) => this._property_str = str
});

var bar = Object.defineProperty({}, 'str', {
  enumerable: true,
  get: () => foo.str + 'bar', 
});

var baz = Object.defineProperty({}, 'str', {
  enumerable: true,
  get: () => bar.str + 'baz', 
});



foo.str = 'foo'
console.log(foo.str) // "foo"
console.log(bar.str) // "foobar"
console.log(baz.str) // "foobarbaz"
foo.str = 'fuu';
console.log(baz.str); // "fuubarbaz"

动态组成的弦

3 个答案: