How to find firebase function running locally or not from code

I wanted to assign a url to firbase functions

const localUrl = localUrlBase + apiEndpoint
const onlineUrl = onlineURLBase + apiEndpoint 
const urlToUse = process.env.dev? localUrl : onlineUrl

Now, when I am running functions locally, I am expecting it assign localUrl but it is assigning onlineUrl

How to know from the code if functions are hosted online or are running locally.

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