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Javascript – Function return undefined

I have a function that return a undefined thing even if it normally need to return something defined.

I have this code with a function :

const GtfsRealtimeBindings = require("gtfs-realtime-bindings");
const fetch = require("node-fetch");
const long = require("long");

async function getTGVStops(tgv_number){

    var answer

    try {
      const response = await fetch("https://proxy.transport.data.gouv.fr/resource/sncf-tgv-gtfs-rt-trip-updates", {
        headers: {
          //"x-api-key": "<redacted>",
          // replace with your GTFS-realtime source's auth token
          // e.g. x-api-key is the header value used for NY's MTA GTFS APIs
        },
      });
      if (!response.ok) {
        const error = new Error(`${response.url}: ${response.status} ${response.statusText}`);
        error.response = response;
        throw error;
        process.exit(1);
      }
      const buffer = await response.arrayBuffer();
      const feed = GtfsRealtimeBindings.transit_realtime.FeedMessage.decode(
        new Uint8Array(buffer)
      );
      feed.entity.forEach((entity) => {
        if (entity.id.includes(tgv_number)) {
          answser = entity.tripUpdate.stopTimeUpdate
          console.log(answser)
          return answser
        }
      })
    }
    catch (error) {
      console.log(error);
      process.exit(1);
    }
}

module.exports = { getTGVStops }

and want to call it in an other files,

const tgv = require("./tgv_information.js")
const station = require("./station.js")
const GtfsRealtimeBindings = require("gtfs-realtime-bindings");

tgv.getTGVStops("6033").then((answer) => { 
    console.log("test")
    console.log(answer); 
});

But it always say undefined.

Tags:

2

Answers


  1. 0

    Because it was written in the definition： var answer
    But using in ：（）

    if (entity.id.includes(tgv_number)) {
          answser = entity.tripUpdate.stopTimeUpdate
          console.log(answser)
          return answser
        }

    so it will be undefied，because you have not define answser, change "answser" to "answer" it will be fixed

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  2. 0

    The return statement you have inside the forEach will return from the closure, not the calling function.

    One approach is to use a straightforward for-of loop instead of a forEach call:

    for (entity of feed.entity) {
  if (entity.id.includes(tgv_number)) {
    answser = entity.tripUpdate.stopTimeUpdate
    console.log(answser)
    return answser
  }
}
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