typescript 函数名末尾的 $ 符号表示什么？
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What does $ sign at the end of function name indicate?
提问by ishandutta2007
Here is the code I'm reviewing...
这是我正在的代码...
import { Observable } from 'rxjs/Rx';
// reducer
import { playerRegister, PlayerState } from './player';
export function getPlayer$ (state$: Observable<MyAppState>): Observable<PlayerState> {
return state$.select(state => state.player);
};
回答by Robby Cornelissen
Syntactically, the dollar ($) character has no special meaning in JavaScript identifiers.
从语法上讲，美元 ( $) 字符在JavaScript 标识符中没有特殊含义。
It is, however, sometimes used by convention to indicate that a variable holds an Observableor that a function will return an Observable.
然而，有时按照惯例使用它来表示一个变量持有一个Observable或一个函数将返回一个Observable。
回答by Matt Burnell
I'm not sure if it's used more widely than within the RxJS community, but within this community it's commonly used to indicate that a variable is a stream (i.e. an Observable) or that a function returns such a stream.
我不确定它是否比在 RxJS 社区中的使用更广泛，但在这个社区中，它通常用于表示变量是一个流（即一个 Observable）或者一个函数返回这样一个流。
回答by ggradnig
This is a code convention named Finnish Notation, apparently due to the origin of the developerthat is attributedfor first using it. It's used to indicate the Observabletype of a variable or function.
这是一个名为Finnish Notation的代码约定，显然是由于首先使用它的开发人员的出身。它用于指示变量或函数的类型。Observable
The idea is that an Observable usually represents a stream of multiple Valuesand a pluralized variable / function name would indicate this. To not be confused with array variables (which are usually also pluralized), the $character is used instead of the s. When reading the variable, you'd read the $as an s.
这个想法是一个 Observable 通常代表一个多个 Value的流，一个复数变量/函数名称将表明这一点。为了不要与数组变量（通常也是复数形式）混淆，使用$字符而不是s. 读取变量时，您会将 读取$为s.
Example
例子
When naming an array, you'll most likely use the proper plural form of a single element's name, as in:
命名数组时，您很可能会使用单个元素名称的正确复数形式，例如：
const pets = ['cat', 'dog', 'turtle']
const pets = ['cat', 'dog', 'turtle']
While, if you had an observable that emitted those three values, you'd use:
同时，如果您有一个发出这三个值的 observable，您可以使用：
const pet$ = from(['cat', 'dog', 'turtle']) // read: pets
const pet$ = from(['cat', 'dog', 'turtle']) // read: pets
It's up to you and your team whether you want to use it. I guess there is no explicit consensus as of now, so you can have a long and meaningful argument about it ;-). There are already tslint rulesavailable that allow you to enforce your decision.
是否要使用它取决于您和您的团队。我想到目前为止还没有明确的共识，因此您可以对此进行长期而有意义的争论;-)。已经有可用的tslint 规则允许您执行您的决定。
