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JavaScript jQuery Basics (2014) Creating a Mobile Drop Down Menu Getting a value

Posted by Dean Pierrot
Dean Pierrot
18,403 Points

Need help with my code please!!!

what am I doing wrong here?

js/app.js 
//Select the input for the title for blog post.
var $titleInput = $("#title");

//Select the preview h1 tag
var $previewTitle = $("#titlePreview");

// Every second update the preview
var previewTimer = setInterval(updatePreview, 1000);

function updatePreview(){ 
  //Get the user's input
  var titleValue = (this);
  $(titleValue).val("#titlePreview");
  //Set the user input as the preview title. 
  $previewTitle.text(titleValue);
}
index.html 
<!DOCTYPE html>
<html>
<head>
  <link rel="stylesheet" type="text/css" href="theme.css">
</head>
<body>
  <div id="form">
    <label for="title">Blog Post Title</label><input id="title" name="title" value="" placeholder="Enter your blog title here">
  </div>
  <div id="preview">
    <h1 id="titlePreview"></h1>
  </div>
  <script src="//code.jquery.com/jquery-1.11.0.min.js" type="text/javascript" charset="utf-8"></script>
  <script src="js/app.js" type="text/javascript" charset="utf-8"></script>
</body>
</html>
theme.css 
  #form {
    width: 45%;
    float: left;
  }
  #preview {
    width: 45%;
    float: right;
  }
  label {
    width: 20%;
    display: inline-block;
  }
  input {
    width: 70%;
  }

2 Answers

Nicolas Hampton
Nicolas Hampton
44,638 Points

In update preview, when you ask for 'this', it's not the title input. You're getting the this context for setInterval, which is actually the window object. setInterval is actually short for:

window.setInterval(updatePreview, 1000);

Keeping track of the context of 'this' in javascript can be tricky. In this case, the value of this is determined by what can be called "implicit binding", which means the value of this will be determined by the object that this is being called by, which is the window. Long story short, that's not going to help you here.

What you want to do is to take that $titleInput variable you've saved, and get the value stored in that element, like:

//Get the user's input
var titleValue = $titleInput.val();
$previewTitle.text(titleValue);

And that should update the preview every second like you're looking to do. Happy coding!

Dean Pierrot
Dean Pierrot
18,403 Points
Dean Pierrot
Dean Pierrot
18,403 Points

Thank you!

Nicolas Hampton
Nicolas Hampton
44,638 Points

No problem, happy coding!