javascript - Why i need to use return keyword in this function so the promise work correctly?

Question

Code:

script1.js:

function getPeople(fetch) {
  fetch('some API').then(res => res.json()).then(data => {
     return {
       count: data.count,
       results: data.results
     }

  })
}

module.exports = getPeople;

script2:

const fetch = require('node-fetch');
const getPeople = require('./script1');

getPeople(fetch).then(data => console.log(data) //TypeError: Cannot read property 'then' of undefined

This error is resolved when add return keyword in getPeople function like this:

function getPeople(fetch) {
  return fetch('some API').then(res => res.json()).then(data => {
     return {
       count: data.count,
       results: data.results
     }

  })
}

I wonder why i need this return keyword before fetch() while i already use it to return data:

 return {
       count: data.count,
       results: data.results
     }

question from:https://stackoverflow.com/questions/66057192/why-i-need-to-use-return-keyword-in-this-function-so-the-promise-work-correctly

Answer 1

If you don't return the promise from your function that fetch() creates, then your function is just returning undefined and NOTHING is communicated back to the caller. You have to return the promise.

The return of your data is a return to the .then() callback. That's not a return from your function. That return is also needed because that sets the resolved value of the parent promise, but that just returns back from the callback into the promise infrastructure and is not a return from your function itself. To return from the function itself, you need a return that isn't nested inside some other function.