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JavaScript Node.js Basics 2017 Building a Command Line Application Parsing JSON

Posted by Sander Heieren
Sander Heieren
12,613 Points

Why can I not see value of body? Only prints out empty string. Does it not get added to the the string for every chunk?

HERE IS THE CODE: 

const https = require("https"); 
const username = 'chalkers'; 
function printMessage(username, badge, points){
  const message = `${username} has ${badge} badges and ${points} points in js`
  console.log(message); 
}
//connect to api
const request = https.get(`https://teamtreehouse.com/${username}.json`, response =>{
  let body = "";
  response.on('data', data =>{
    body += data.toString();
  })
  //response.on('end', () =>{
              //console.log(body); 
  //            })
  console.log(body); // THIS ONE HERE. WHY DOES IT NOT GET ADDED TO BODY? 
});
Sander Heieren
Sander Heieren
12,613 Points

very sorry for bad formatting...

Rich Donnellan
Rich Donnellan
Treehouse Moderator 27,708 Points
Rich Donnellan
Rich Donnellan
Treehouse Moderator 27,708 Points

Question updated with code formatting. Check out the Markdown Cheatsheet below the Add an Answer submission for syntax examples, or choose Edit Question from the three dots next to Add Comment to see how I improved the readability.

1 Answer

James Crosslin
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
James Crosslin
Full Stack JavaScript Techdegree Graduate 16,882 Points
James Crosslin
.a{fill-rule:evenodd;}techdegree seal-36
James Crosslin
Full Stack JavaScript Techdegree Graduate 16,882 Points

The answer is because it only console logs once and before any data is returned. Your 'get' request is an asynchronous function. It sends out a request and body exists as an empty string until you start getting responses. But your console.log(body) method does not understand that. Console.log(body) is next on the call stack before the data returns, so it runs one time and returns the value of body, which is an empty string. If you want to console log each stage of the body concatenation, you can do this:

const https = require("https")
const username = "chalkers"

function printMessage(username, badgeCount, points) {
  const message = `${username} has ${badgeCount} badges and ${points} points in JavaScript`
  console.log(message)
}
//Connect to the API URL (https://teamtreehouse.com/username.json)

const request = https.get(
  `https://teamtreehouse.com/${username}.json`,
  (response) => {
    let body = ""
     response.on("data", (data) => {
      body += data.toString()
      console.log(body)  // <--- This is where you have to place your log
    })
  }
)

This will print the entirety of your body variable each time a new round of data comes in. Your console.log(body) has to be within the scope of the data transmission and reception method, '.on()'.