Javascript 接口中的 TypeScript 可选函数
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/27522973/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
TypeScript Optional function in Interface
提问by Anton Selin
Is it possible to create an Interface in TypeScript with optional function?
是否可以在带有可选功能的 TypeScript 中创建接口？
interface IElement {
name: string;
options: any;
type: string;
value?: string;
validation(any): boolean; // --> should be optional.
}
回答by Gone Coding
There are currently three syntaxes that TypeScript allows for function declarations in interfaces:
目前 TypeScript 允许在接口中声明函数的三种语法：
Using your example of a validationfunction taking 1 parameter (of anytype) and a booleanreturn value:
使用带有validation1 个参数（any类型）和boolean返回值的函数示例：
validation: {(flag: any): boolean};
or in the newer syntax:
或使用较新的语法：
validation(flag: any) : boolean;
or an alternative is:
或者替代方案是：
validation: (flag: any) => boolean;
Solution:
解决方案：
so to make it optional with the old syntax is easy:
所以用旧的语法使它成为可选的很容易：
validation?: {(flag: any): boolean};
with the second syntax (recent addition - thanks to @toothbrush)
使用第二种语法（最近添加 - 感谢@toothbrush）
validation?(flag: any) : boolean;
or in the third syntax (as you found):
或在第三种语法中（如您所见）：
validation?: (flag: any) => boolean;
