Optional is not quite the same as `| undefined` about modern-typescript-with-examples-cheat-sheet HOT 3 CLOSED

Cheers! I made an update, what do you think?

Optional parameter ? automatically adds | undefined

type User = {
  firstName: string;
  lastName?: string; // same as `string | undefined`
};

In JavaScript, every function parameter is optional, when left off their value is undefined. We can get this functionality in TypeScript by adding a ? to the end of parameters we want to be optional. This is different from adding | undefined which requires the parameter to be explicitly passed as undefined

function fn1(x: number | undefined): void {
  x;
}

function fn2(x?: number): void {
  x;
}

fn1(); // Error
fn2(); // OK
fn1(undefined); // OK
fn2(undefined); // OK

from modern-typescript-with-examples-cheat-sheet.

Looks good!

from modern-typescript-with-examples-cheat-sheet.

Cool. I will close the issue, thanks again for your feedback.

I just added a ton more examples and did a lot of re-writing, so even more feedback is welcome!

from modern-typescript-with-examples-cheat-sheet.