Typewriter Script

3rd February 2009 - 2 minutes read time

Note: This post is over a year old and so the information contained here might be out of date. If you do spot something please leave a comment and I will endeavour to correct.

The following script can be used if you want to simulate a typewriter in an element on screen. I have put in a lot of comments to describe what is happening but the script works by taking each array element in turn and adding it character by character to the content of the selected element.

<script type="text/javascript">
// set up text to print, each item in array is new line
var aText = new Array(
"line 1",
"line 2",
"line 3",
"line 4",
"line 5",
"    ",
"line 7",
"line 8",
"THE END "
);
var iSpeed = 100; // time delay of print out
var iIndex = 0; // start printing array at this posision
var iArrLength = aText[0].length; // the length of the text array
var iScrollAt = 20; // start scrolling up at this many lines
 
var iTextPos = 0; // initialise text position
var sContents = ''; // initialise contents variable
var iRow; // initialise current row
 
function typewriter()
{
 sContents =  ' ';
 iRow = Math.max(0, iIndex-iScrollAt);
 var destination = document.getElementById("typedtext");
 
 while ( iRow < iIndex ) {
  sContents += aText[iRow++] + '<br />';
 }
 destination.innerHTML = sContents + aText[iIndex].substring(0, iTextPos) + "_";
 if ( iTextPos++ == iArrLength ) {
  iTextPos = 0;
  iIndex++;
  if ( iIndex != aText.length ) {
   iArrLength = aText[iIndex].length;
   setTimeout("typewriter()", 500);
  }
 } else {
  setTimeout("typewriter()", iSpeed);
 }
}
</script>

You can run this script by either including an onload attribute in the body tag, or by placing a call to the typewriter() function after the element that you want to use to fill the text with.

<div id="typedtext"></div>
<script type="text/javascript">typewriter();</script>

JavaScript

Comments

Permalink

Nice - Line 29 you're missing the end of the quotes - sContents += aText[iRow++] + ' ';

Permalink

Yup, I had forgotten to encode the
tag at the end of that line. I've fixed that now.

Add new comment

Related Content

Using Shadow DOM

When I first heard the term "Shadow DOM" I had to laugh at the name. I had visions of a cloak and dagger HTML element that would only be seen on the dark web. Or some sort of nefarious shadow site that was the after effect of a hack. In reality, this is quite a useful bit of technology that has a number of applications, although it does need a fairly modern browser to be able to use it. Shadow DOM is part of the web components strategy, which includes custom elements and HTML templates. These give developers the power to create custom tools and experiences that are encapsulated away from other parts of the code. In this article I will go though what the shadow DOM is, how to use it, and in what situations it comes in handy.

Simple Horizontal Segmented Bar Chart With CSS

Bar charts are powerful ways to show the relationships between different data items. If the data you want to show is discrete then a simple horizontal segmented bar chart is a good idea. You can easily change a collection of numbers into a related set of attributes.

Inspecting And Reusing jQuery Events

Adding events to HTML elements with jQuery is pretty simple, but I found that extending those events wasn't an easy task. I was faced with an issue where I had some third party code that performed an action on an element, and I needed to add an event and call the same handler from that event. As this was within a CMS I had limited scope to just add my new event to the existing code, so I needed a way of pulling out the current jQuery events and then calling that event handler separately. This post looks at how I accomplished this.

Langton's Ant In JavaScript

After looking at Conway's game of life I have been looking at other forms of cellular automata. This lead me to discover Langton's ant, which is a different kind of cellular automata where an agent (namely an ant) is used to turn the squares on or off as it travels around a grid.

The rules of Langton's ant are quite simple. The ant simply follows two rules as it moves around the grid.

Adventures In FizzBuzz

Tests for programmers in an interview process are not uncommon. For the last couple of years I have asked a quick pre-interview question to junior developers to see what sort of stuff they come up with.

As I don't want to set any developer a task that will take longer than absolutely needed I opted to set a very simple task for them. Commonly known as "FizzBuzz", this task is as follows.

Checking If An Element Exists In jQuery

To verify that an element exists in the DOM you just need to use the .length property of a jQuery lookup. If the element is there then the number of elements found will be greater than 0.