Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript Loops, Arrays and Objects Tracking Data Using Objects The Build an Object Challenge, Part 2

Feedback on solution please

//Array of student objects

let students = [

  {
    name: "Manuel",
    track: "Python",
    acheivements: 30,
    points: 1560,
  },

  {
    name: "Jose",
    track: "Javascript",
    acheivements: 23,
    points: 450,
  },

  {
    name: "Sarah",
    track: "HTML",
    acheivements: 53,
    points: 1890,
  },

  {
    name: "Tess",
    track: "C+",
    acheivements: 2,
    points: 67,
  },

  {
    name: "Coolio",
    track: "PHP",
    acheivements: 56,
    points: 2013,
  },

];

//Sets output as empty string and selects <div> with id="output"
let output = ''
let html = document.querySelector("#output");


//Iterates through each student object in the students array
for ( let student in students ) {

//  Iterates through each key-value pair in the current student object
  for ( let key in students[student] ) {

//      Puts current value in a variable for readability and capitalises first letter of the key
      let value = students[student][key];
      let keyCapitalized = key.charAt(0).toUpperCase() + key.slice(1);

//      Puts each name key-value pair as a <h2> and all other pairs as <p> and adds to output string 
      if ( key === 'name' ) {
          output += `<h2><strong>${keyCapitalized}: ${value}</strong></h2>`;
      } else {
        output += `<p>${keyCapitalized}: ${value}</p>`;
      }
  }

//  Line break after each student object
  output += '<br>'

}


// Writes the output string into the HTML
html.innerHTML = output;

2 Answers

Steven Parker
Steven Parker
229,670 Points

Iterating through the properties can be a useful technique But you should be aware of some behavioral differences from the original code that will occur:

  • if a property is missing, it will be silently omitted where the original will show the property as "undefined"
  • if any extra properties are added, they will be listed where the original would show only the intended ones
  • the order that the properties are listed is no longer guaranteed

Thanks for the feedback, do I understand correctly?:

  • So basically if you want the ability to alter things in the students array and have these changes reflected in the HTML this is the way to go.
  • But if you want the output to always reflect the initial array regardless of subsequent changes I should use another method?

Also can you explain why the order is not guaranteed? I thought a for .. in loop always iterated from first to last

Steven Parker
Steven Parker
229,670 Points

What I meant was that the original method could output the properties in a specific order each time regardless of what the class structure was like.

Nice way to see the problem!