javascript 如何在我的 React Component 类中拥有类范围的常量？
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How can I have class-wide constant in my React Component class?
提问by notalentgeek
Usually I do this:
通常我这样做：
var tagSymbols = Object.freeze([
'!',
'+',
'@'
]);
But then I know there is constfrom Babel (?).
但后来我知道有const来自 Babel (?)。
const tagSymbols = Object.freeze([
'!',
'+',
'@'
]);
Both return the same error:
两者都返回相同的错误：
Syntax error: Unexpected token (4:6)
2 |
3 | class GeneralToDoListInput extends Component {
> 4 | var tagSymbols = Object.freeze([
| ^
5 | '!',
6 | '+',
7 | '@'
Syntax error: Unexpected token (5:8)
3 | class GeneralToDoListInput extends Component {
4 |
> 5 | const tagSymbols = Object.freeze([
| ^
6 | '!',
7 | '+',
8 | '@'
回答by Felix Kling
You cannot put variable declarations inside a class body. That's just not allowed by the language. In ES6, the structure of a class declaration is basically
您不能将变量声明放在类体内。这是语言所不允许的。在 ES6 中，类声明的结构基本上是
class Foo() {
method1() {}
method2() {}
...
}
The simplest solution would be to put the variable declaration outside of the class:
最简单的解决方案是将变量声明放在类之外：
const tagSymbols = ...:
class GeneralToDoListInput extends Component {
...
}
Any code inside the class/module can access tagSymbols.
类/模块中的任何代码都可以访问tagSymbols.
If it really has to be a class property you can either define a static getter:
如果它真的必须是一个类属性，你可以定义一个静态 getter：
class GeneralToDoListInput extends Component {
static get tagSymbols() {
return Object.freeze(...);
}
}
Or assign it to the class after the declaration:
或者在声明后将其分配给类：
class GeneralToDoListInput extends Component {
...
}
GeneralToDoListInput.tagSymbols = ...;
