Added undefined as required

[r-khr]

Related to this issue: Error FromGroupState property undefined with validation required #64

[MrWolfZ]

Thank you for this PR. Please rebase your change onto develop and target develop with this PR (you'll have to perform a npm install since the dependencies have changed on develop compared to master). Also please update the inline comment of the required function to mention that the value must be non-undefined (i.e. adjust line 4 in required.ts).

[r-khr]

Updated and rebased!

[MrWolfZ]

Please fix the issues I pointed out in my comments.

[MrWolfZ]

Please mention both null and undefined, i.e. "A validation function that requires the value to be non-null, non-undefined, and non-empty."

[MrWolfZ]

To support strict type checking you need to make it explicit that the function accepts undefined as a value, i.e.

export function required<T>(value: T | null | undefined): ValidationErrors {

This will also fix the TSLint error.

[MrWolfZ]

Thanks for the update. As you can see here there is a TSLint error. Have a look at my inline comments for what needs to be changed.

[r-khr]

Thanks for the review, I updated as requested.