TypeScript 变量作用域

Question

所以我最近开始使用 TypeScript，到目前为止我很享受它，但是有一个问题我就是无法理解为什么它不能正常工作。

"var" 关键字仍然可以自然地在 TypeScript 中访问，我知道它是一个函数范围，而不是 "let" 关键字的块范围。我有以下代码，但我不明白为什么它不起作用：

 class Calendar {
      month: number;
      months: string[];
      weekday: number;
      day: number;
      constructor() {
        this.month = date.getMonth();
        this.months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'November', 'December'];
        this.weekday = date.getDay();
        this.day = date.getDate();
      }
      nextMonth() {
        var months = this.months;
        var currentmonth: number = this.month;

        el('.icono-caretRight').addEventListener('click', () => {
          currentmonth = (currentmonth + 1) % months.length;
        }, false);

        month = currentmonth;
        return month;
      }
      previousMonth() {
        el('.icono-caretLeft').addEventListener('click', () => {
          month--;
        }, false);
      }
    }

let calendar = new Calendar();
let month = calendar.month;
let nextmonth = calendar.nextMonth();
console.log(nextmonth);

查看 nextMonth() 函数。我不知道为什么 "month" 变量没有增加。我到底做错了什么？

注意：我使用的是 JSPM + TypeScript（插件类型脚本）。

提前致谢！

Answer 1

the "var" keyword is still accessible in TypeScript naturally and I know that it's a function scope, versus block scope for the "let" keyword. I have the following code and I can't figure out why it's not working:

您对scoping的理解是正确的。

以下代码有效：

class Calendar {
      month: number = 0;
      months: string[];

      constructor() {
        this.months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'November', 'December'];
      }
      nextMonth() {
        var months = this.months;
        var currentmonth: number = this.month;
        currentmonth = (currentmonth + 1) % months.length;
        month = currentmonth;
        return month;
      }
    }

let calendar = new Calendar();
let month = calendar.month; // 0
let nextmonth = calendar.nextMonth();
console.log(nextmonth); // 1

我怀疑您对 month 与 this.month 和/或 addEventListener 与 实际调用函数 感到困惑。

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根据用户评论：

I understand that the this.month is 0 since well the date.getMonth() is actually 0. My problem in that is doesn't want to increment, probably I don't get the addEventListener part of the function or maybe like you said I'm confused, because it's suppose to increment on click correct? It has to return a new value everytime the user clicks right? Or... Not sure anymore though

密码

el('.icono-caretRight').addEventListener('click', () => {
          currentmonth = (currentmonth + 1) % months.length;
        }, false);

可能是您想在 构造函数 中执行的操作。您很可能想要：

el('.icono-caretRight').addEventListener('click', () => {
   this.nextMonth();
}, false);

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