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Handling Errors - Solution

2:34 with Andrew Chalkley

In this video I'll show you how I added error handling all throughout my application.

Documentation

OpenWeatherMap API Solution Code

Here's an overview of the differences from the code shown in the video:

  • weather.js
    • There's no need to create a readable query as the query value that's being passed into the method is already in a readable format
    • There's no need to check if the location was found as the API won't return a "200" OK status code if the query wasn't successful

Here's the code:

weather.js
const http = require('http');
const https = require('https');
const querystring = require('querystring');
const api = require('./api.json');

// Print out temp details
function printWeather(weather) {
  const message = `Current temperature in ${weather.name} is ${weather.main.temp}F`;
  console.log(message);
}

// Print out error message
function printError(error) {
  console.error(error.message);
}

function get(query) {
    try {
      const parameters = {
        APPID: api.key,
        units: 'imperial'
      };

      const zipCode = parseInt(query);
      if (!isNaN(zipCode)) {
        parameters.zip = zipCode + ',us';
      } else {
        parameters.q = query + ',us';
      }

      const url = `https://api.openweathermap.org/data/2.5/weather?${querystring.stringify(parameters)}`;
      console.log(url);

      const request = https.get(url, response => {
        if (response.statusCode === 200) {
          let body = '';
          // Read the data
          response.on('data', chunk => {
            body += chunk;
          });
          response.on('end', () => {
            try {
              //Parse data
              const weather = JSON.parse(body);
              //Print the data
              printWeather(weather);
            } catch (error) {
              //Parser error
              printError(error);
            }
          });
        } else {
          // Status error code
          const statusErrorCode = new Error(`There was an error getting the message for "${query}". (${http.STATUS_CODES[response.statusCode]})`);
          printError(statusErrorCode);
        }        
      });
    } catch (error) {
      printError(error);
    }  
}

module.exports.get = get;
  • 0:01

    First I implemented a printError function

  • 0:04

    that will display the message from the error object.

  • 0:08

    I used a try catch statement in case if the URL is malformed.

  • 0:13

    Remember, if a malformed URL is entered,

  • 0:17

    the error will be thrown immediately and not emitted.

  • 0:21

    In the catch block, I called the print error function for the malformed error.

  • 0:28

    Then I checked the status code was okay or 200.

  • 0:33

    Here, I created an error message with a human readable status message.

  • 0:39

    Remember, STATUS_CODES object is only on HTTP, not HTTPS.

  • 0:48

    I've also included a readable query, adding spaces back in to the query.

  • 0:55

    The code for

  • 0:56

    the readable query is up here, because I may need it for other errors later on.

  • 1:01

    Next I catch any thrown errors by the JSON parser.

  • 1:06

    Finally if the query doesn't return a location because it's spelt wrong, or

  • 1:11

    the place doesn't exist, we want to return a sensible error message.

  • 1:19

    Let's see this in action.

  • 1:21

    Type node app.js 90210.

  • 1:28

    And then a location.

  • 1:35

    And then somewhere fictional.

  • 1:48

    And we get that sensible error message.

  • 1:50

    Cool.

  • 1:52

    Great work, you've come a long way.

  • 1:54

    You should be really proud of yourself.

  • 1:56

    You've created two command line applications that go out on to

  • 1:59

    the Internet and retrieve information.

  • 2:01

    Now that you've worked with two API endpoints, you can use any.

  • 2:06

    The possibilities are endless.

  • 2:08

    Why not make a command line utility that goes out to Twitter and

  • 2:12

    brings back the latest tweets from your favorite JavaScript developer?

  • 2:16

    Or get the latest stock prices for your favorite tech company?

  • 2:19

    Or a command line application that converts currencies?

  • 2:23

    I encourage you to practice more to really solidify the concepts.

  • 2:26

    Looking at the documentation and other solutions isn't cheating.

  • 2:30

    They're aids for your learning.

  • 2:32

    Until next time, keep practicing.

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