How to simplify simple statement in typescript or js

Question

I would like to simplify this expression but don't know how. There has to be a way to have the same expression without the three conditions.

if ( request.Document != null &&
      request.Document != undefined &&
      request.Document != "" )

Just for context I am talking something similar to c#'s !string.isNullOrEmpty()

As a a value other than any of those outline is considered truthy when coerced in JS, you can just use `if (request.Document) { ...` — Rory McCrossan, Sep 23 '22 at 09:17
What will happen if the string is empty ("")? @RoryMcCrossan — MatejDodevski, Sep 23 '22 at 09:18
`x != undefined` <-- Don't do this; you should use `typeof x === 'undefined'` instead. — Dai, Sep 23 '22 at 09:19
you can simply write ```if ( request.Document ) { ..... }``` This will return false for empty string, undefined, null and 0 as number — Srushti Shah, Sep 23 '22 at 09:19
@MatejDodevski you may consider `if(request.Document?.trim())` as in `isNullOrWhitespace()`. Besides that, you should get familiar with [Truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy) and [Falsy](https://developer.mozilla.org/en-US/docs/Glossary/Falsy) values in JS. — Thomas, Sep 23 '22 at 09:24

score 1 · Accepted Answer · answered Sep 23 '22 at 09:19

1

if (request.Document) {
  ...
}

as null, undefined, '' will all return false.

(but [], {} or ' ' will return true)

Check the equality table for more info about other values.

answered Sep 23 '22 at 09:19

Matthieu Riegler

_"but `[]`, `{}` or `' '` will return `true`"_ - right, so to handle those cases methinks it would be sensible to use `if( ( typeof request.Document === 'string' ) && /^\w+$/.test( request.Document ) ) { ... }` (assuming that regex is okay). – Dai Sep 23 '22 at 09:29

1 Answers1