Typescript 参数名称中的问号是什么
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What is the question mark for in a Typescript parameter name
提问by Whisher
export class Thread {
id: string;
lastMessage: Message;
name: string;
avatarSrc: string;
constructor(id?: string,
name?: string,
avatarSrc?: string) {
this.id = id || uuid();
this.name = name;
this.avatarSrc = avatarSrc;
}
}
In id?what's the ?for?
是为了id?什么?？
回答by Fidan Hakaj
It is to mark the parameter as optional.
是将参数标记为可选。
回答by DvG
This is to make the variable of Optional type.Otherwise declared variables shows "undefined" if this variable is not used.
这是为了使变量为 Optional 类型。否则，如果未使用此变量，则声明的变量将显示“未定义”。
export interface ISearchResult {
title: string;
listTitle:string;
entityName?: string,
lookupName?:string,
lookupId?:string
}
回答by Masih Jahangiri
parameter?: typeis a shorthand for parameter: type | undefined
parameter?: type是一个简写 parameter: type | undefined
