Object 可能是可选链接上的“未定义”错误 Typescript

Question

I have a response which I am accessing: data?.currentOrganization?.onboardingSteps? . As you can guess, data, currentOrganization, and onboardingSteps might all be null. I want to assign a variable as follows:

const hasSteps = data?.currentOrganization?.onboardingSteps?.length > 0;

I thought hasValue would evaluate to false if any of the fields were null or if there was less than 1 step. However, I get the TypeScript error: Object is possibly 'undefined' .

This is how I am currently getting around it:

const hasSteps =
  data?.currentOrganization?.onboardingSteps != null &&
  data?.currentOrganization?.onboardingSteps?.length > 0;

This feels unnecessarily verbose. Is there an alternative, more elegant solution?

Answer 1

The optional chain will end up producing a value for data?.currentOrganization?.onboardingSteps?.length which is presumably a number if everything in the chain is not null or undefined .... but if anything in the chain is nullish, then the output will be undefined itself. You can't test undefined > 0 without Typescript complaining about it.

So you should probably do something like the following:

const hasSteps = (data?.currentOrganization?.onboardingSteps?.length ?? 0) > 0;

This is using nullish coalescing to produce 0 if the optional chain ends in undefined .

Playground link to code