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JavaScript Object-Oriented JavaScript (2015) Constructor Functions and Prototypes Making the UI Work

Lido Fernandez
Lido Fernandez
10,556 Points
Posted by Lido Fernandez
Lido Fernandez
10,556 Points

Someone please can send/provide me a message/link with the explanation of this method?: renderInElement

I use it for the built the PlayList Challenge but I still do not get what it does.

3 Answers

LaVaughn Haynes
LaVaughn Haynes
12,397 Points
LaVaughn Haynes
LaVaughn Haynes
12,397 Points

In the HTML you have an ordered list <ol> with an id of "playlist".

<div>
  <h1>Treetunes</h1>

  <ol id="playlist">
  </ol>

  <button id="play">Play</button>
  <button id="next">Next</button>
  <button id="stop">Stop</button>

</div>

We can grab that ordered list element and store it as the variable playlistElement, and then pass it to renderInElement

var playlistElement = document.getElementById("playlist");
playlist.renderInElement(playlistElement);

renderInElement deletes anything in the the ordered list and then loops through all of the songs, generates the appropriate HTML for each song and puts it inside the ordered list. Think of it as updating the playlist on the screen. It deletes the old rendering of the list and redraws it.

Playlist.prototype.renderInElement = function(list) {
  //delete any html inside the our ordered list by setting it to an empty string
  list.innerHTML = "";

  //loop through each song
  for(var i = 0; i < this.songs.length; i++) {
    //generate an HTML element for each song and put it inside the ordered list
    //toHTML() explained below
    list.innerHTML += this.songs[i].toHTML();
  }
};

This is the part that generates HTML for each song. As you see it makes a list element <li> which contains information for a song

Song.prototype.toHTML = function() {
  var htmlString = '<li';
  if(this.isPlaying) {
    htmlString += ' class="current"';
  }
  htmlString += '>';
  htmlString += this.title;
  htmlString += ' - '
  htmlString += this.artist;
  htmlString += '<span class="duration">'
  htmlString += this.duration;
  htmlString += '</span></li>';
  return htmlString;
};

Hopefully this helps. You can also re-watch where he talks about around the 2 minute mark here https://teamtreehouse.com/library/objectoriented-javascript/constructor-functions-and-prototypes/making-the-ui-work

isral duke
isral duke
7,315 Points
isral duke
isral duke
7,315 Points

i had the same question as Lido. After some thought i finally realized that the array's contents (all of the elements in the array) have to be output to HTML. Sometimes it helps to think about the code for a while to make it click in the greybox.