Typescript Optional Function In Interface

Is it possible to create an Interface in TypeScript with optional function? interface IElement { name: string; options: any; type: string; value?: string; validation(any)

Solution 1:

There are currently three syntaxes that TypeScript allows for function declarations in interfaces:

Using your example of a validation function taking 1 parameter (of any type) and a boolean return value:

validation: {(flag: any): boolean};

or in the newer syntax:

validation(flag: any) : boolean;

or an alternative is:

validation: (flag: any) =>boolean;

Answer :

so to make it optional with the old syntax is easy:

validation?: {(flag: any): boolean};

with the second syntax (recent addition - thanks to @toothbrush)

validation?(flag: any) : boolean;

or in the third syntax (as you found):

validation?: (flag: any) =>boolean;