Optional class members in Typescript

Question

Is there a way to specify type-safe optional members in Typescript classes?

That is, something like...

class Foo {     a?: string;     b?: string;     c: number; }  ....  foo = new Foo(); ... if (foo.a !== undefined) { ... (access foo.a in a type-safe string manner) ... } 

In case you are familiar with OCaml/F#, I am looking for something like 'string option'.

Answer 1

The following works in TypeScript 3.x:

class Foo {   a?: string;   b?: string;   c: number = 123; } 

Note that you need to initialise any members that are not optional (either inline as shown or in the constructor).