关于javascript：TypeScript var scoping

TypeScript var scoping

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，我就是不明白它为什么不能正常工作。

"var"关键字在typescript中仍然可以自然访问，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，但我不明白它为什么不能工作：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33

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"变量没有递增。我到底做错了什么？

注意：我使用的是jspm+typescript(插件类型脚本)。

事先谢谢！

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:

你对scoping的理解是正确的。

以下代码确实有效：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

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

我怀疑你对monthvs.this.month和/或addEventListenervs.实际调用函数感到困惑。

根据用户意见：

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

代码

1
2
3

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

可能是您要在构造函数中执行的操作。很可能你想要：

1
2
3

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