javascript - 将方法添加到字符串变量的原型(prototype)

Question

预期:当使用 createGreetable 创建变量时，它应该具有由 greetable(text) 设置的附加属性 greet。通常的 string 方法应该仍然可以在此变量上调用。

我尝试过的:

const greetablePrototype = {
  greetable: function(greeting) {
    this.greet = `${greeting}, ${ this.valueOf() }!`
  }
}

function createGreetable(str) {
  const result = new String(str);
  Object.setPrototypeOf(result, greetablePrototype)
  return result;
}

const t = new createGreetable("world");
t.greetable("hello");
console.log(t.greet);

console.log(t.length);

输出:

hello, [object String]!
5

预期输出:

hello, world!
5

Answer 1

您可以扩展字符串类:

class Greetable extends String {
  greet (greeting) {
    return `${greeting}, ${this}!`;
  }
}

const g = new Greetable('world');
g.greet('hello'); // hello, world!
g.length // 5