Replace functions returning explicit undefined value

[gildub]

Undefined means no value has been assigned where null means an empty value.
It's a good practice to return and propagate a null value instead of using undefined because it requires to handle the special type case of undefined in the caller.

[helio-frota]

I would add this practice as well:

before

if (num === undefined) {
  return "";
}
return String(num);

after

if (!num) {
  return "";
}
return String(num);

or more fancy

export const numStr = (num: number | undefined): string => String(num ?? "");

console.log(numStr(1));
console.log(numStr(0));
console.log(numStr(undefined));

ts-playground

[carlosthe19916]

I am not a fan of generic rules applied without reasoning. If there is a specific block of code where we consider we can achieve better readability, usability, performance, etc. then let's do it; let's open a PR and we can discuss what we are solving with that code change.

[helio-frota]

I think this is related with @gildub issue description to avoid runtime error reactwg/react-18#75
the idea is to delegate the check to the lint as trustify-ui is using react 18.

[helio-frota]

For this we would need to enable the lint https://github.com/trustification/trustify-ui/blob/main/.github/workflows/ci-actions.yaml#L29
and add the suggested rules on https://github.com/trustification/trustify-ui/blob/main/.eslintrc.cjs#L40

    "consistent-return": "error", ( or warn ?)
    "no-unused-expressions": "error", ( or warn ?)

I have no idea if there are other rules for this, react-related