覆盖 Javascript 对象中的空字符串

Question

我需要子 class StringBuilder 将字符串传递给父 class 并调用 minus 方法。除非我不在构造函数中对字符串进行硬编码，否则以下代码不起作用。对于数字，这很好用。为什么它不覆盖字符串？或者也许我做的一切都完全错误？

class Builder {
    constructor() {
        this.int = 0
        this.str = ''
    }

    minus(...n) {
        this.int = n.reduce((sum, current) => sum - current, this.int)
        this.str = this.str.slice(0, -n)
        return this
    }
}

class IntBuilder extends Builder {
    constructor(int) {
        super(int)
    }
}

class StringBuilder extends Builder {
    constructor(str) {
        super(str)
    }
}

let number = new IntBuilder()
number.minus(100, 99)

console.log(number)

let string = new StringBuilder('Hello')

string.minus(2)

console.log(string)

Answer 1

您的 Builder 构造函数不带任何参数。声明一个参数并将该参数分配给 this.str。你可以使用 default parameters 来确保它被初始化为你想要的任何东西，即使在没有参数的情况下调用构造函数。

class Builder {
  constructor(str = "") {
    this.int = 0
    this.str = str
  }

  minus(...n) {
    this.int = n.reduce((sum, current) => sum - current, this.int)
    this.str = this.str.slice(0, -n);
    return this;
  }
}

class IntBuilder extends Builder {
  constructor(int) {
    super(int)
  }
}

class StringBuilder extends Builder {
  constructor(str) {
    super(str)
  }
}

let number = new IntBuilder()
number.minus(100, 99)

console.log(number)

let string = new StringBuilder('Hello')

string.minus(2)

console.log(string)

覆盖 Javascript 对象中的空字符串

Overwrite empty string in Javascript object

javascript

string

object