字符串的动态组合

Question

是否有可能以某种方式动态地组成一个字符串？我读过一些关于按值传递和按引用传递的内容，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

提前致谢！

Answer 1

不，当您像那样静态定义事物时，它们将在调用时使用变量。你可以用 getters 做这样的事情：

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`

之所以如此有效，是因为吸气剂的魔力；您不是静态定义属性，而是定义一个在尝试访问属性时调用的函数。这样它就可以 "react" 任何下游更改，因为它总是动态生成的。

Answer 2

这样不行，拼接foo.str +只执行了一次，加号不是调用多次的函数

一种方法是创建一个包含 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

根据 puddi 的回答，我想到了这个：

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"

字符串的动态组合

Dynamic composition of strings

javascript

string

dynamic

composition