What's the simplest Typescript idiom for checking if an array exists and has nonzero length?-CodePudding

I frequently have a collection that might be either undefined or empty. So I write this:

if ((thingies?.length ?? 0) > 0) ...

I guess that's not so bad in the grand scheme, but it ain't pretty. What I really want is a Bash-like operator that means "this variable exists, is an array, and has at least one element":

if (thingies#) ... // it's safe to access thingies[0]

Pretty sure that's not a thing. But what's the most concise Typescript expression of this?

CodePudding user response：

Considering that both undefined and 0 are falsy values, you can just write:

if (array?.length)

Either array is undefined and this will return false, or it is defined and it will return false if length === 0.

CodePudding user response：

I would simply write it like this:

if (Array.isArray(thingies) && thingies.length > 0) {
  [...]
}

Not the shortest way but way more clear (and more correct) in my opinion.

Edit:

If it feels too long and you need it often, you can also simply define it as a function:

import {isNonEmptyArray} from "./utils";

if (isNonEmptyArray(thingies)) {
  [...]
}

// utils.ts
export const isNonEmptyArray = (array: unknown): array is unknown[] => (
  Array.isArray(array) && array.length > 0
)