how to get API data out of a node.js function

Question

I'm pretty new to JS and very very new to Node. I'm trying to make a very simple app that pulls JSON data from the edamam API (https://rapidapi.com/edamam/api/edamam-nutrition-analysis). I've got the API working, and I now want to use the data that the request returns, but it's stuck inside a callback function and I can't figure out how to access it outside of the function that retrieves it.

From what I can tell, it's something to do with the async nature of Node. I've tried re-ordering it in every way I can think of (for over 6 hours!), but all I ever get is undefined variables. I'm figuring that's because they haven't been set yet, but I don't quite have enough of a handle on callback functions to understand how to fix this.

Eventually I want to be able to use the JSON data to update the contents of HTML elements.

   const unirest = require('unirest');


   var getNutritionInfo = {
        mkString: function(foodStr){
          var ingredients = new Array();
          ingredients.push(foodStr);
          console.log(foodStr)
              params = {
              ingr: ingredients,

          };

          esc = encodeURIComponent;
          query = Object.keys(params)
              .map(k => esc(k) + '=' + esc(params[k]))
              .join('&');

          foodQuery = query.replace(/%20/g,"+");
          return(foodQuery);
        },

        analyse: function(foodStr){
          var cals;
          url = "https://edamam-edamam-nutrition-analysis.p.rapidapi.com/api/nutrition-data"
          searchQuery = getNutritionInfo.mkString(foodStr);
          function requestData(callback){
              unirest.get(url+"?" + searchQuery)
              .header("X-RapidAPI-Key", "c5c219c7b0mshbf5b602f68caddep1cd8cfjsn01a1be1f45a4")
              .end(function (result) {
                cals = result.body.totalNutrients.ENERC_KCAL.quantity;
                console.log(cals + " first");
                callback();

            });
          }
          requestData(function(){
            console.log(cals + " second");

                getNutritionInfo.getData();


          });
        },

        getData: function(){
          var calories = getNutritionInfo.analyse.cals;
          console.log(calories + " third");
          return calories;
        }
};

the final console.log is ALWAYS undefined, whereas I am wanting it to return the value on line of cals (result.body.totalNutrients.ENERC_KCAL.quantity);

Also, I'm very sorry. I'm aware that there must be cleaner ways to organise functions and format code. I'll get there eventually :)

Answer 1

the final console.log is ALWAYS undefined, whereas I am wanting it to return the value on line of cals (result.body.totalNutrients.ENERC_KCAL.quantity);

This is because of the asynchronous nature of the nodejs. To get value from requestData(), you need to pass cal as a value to the callback.

Making those changes,

'use strict';

const unirest = require('unirest');

var getNutritionInfo = {
  mkString: function (foodStr) {
    var ingredients = new Array();
    ingredients.push(foodStr);
    console.log(foodStr)
    params = {
      ingr: ingredients,

    };

    esc = encodeURIComponent;
    query = Object.keys(params)
      .map(k => esc(k) + '=' + esc(params[k]))
      .join('&');

    foodQuery = query.replace(/%20/g, "+");
    return (foodQuery);
  },

  analyse: function (foodStr) {
    url = "https://edamam-edamam-nutrition-analysis.p.rapidapi.com/api/nutrition-data"
    searchQuery = getNutritionInfo.mkString(foodStr);
    function requestData(callback) {
      unirest.get(url + "?" + searchQuery)
        .header("X-RapidAPI-Key", "c5c219c7b0mshbf5b602f68caddep1cd8cfjsn01a1be1f45a4")
        .end(function (result) {
          let cals = result.body.totalNutrients.ENERC_KCAL.quantity;
          console.log(cals + " first");
          callback(cals); // pass value here
        });
    }
    requestData(function (cals) { // get value after completion
      console.log(cals + " second");
      getNutritionInfo.getData();
    });
  },

  getData: function () {
    var calories = getNutritionInfo.analyse.cals;
    console.log(calories + " third");
    return calories;
  }
};