JS

JavaScript Demos:
LED Scrolling Banner.

jim.cerny@unh.edu   13-JAN-1998

Discussion.

This is taken from Doug Popeney's collection of JavaScripts, with some minor tweaking and reformatting. It is a complex script and I have not tried to understand its internals in complete detail. I leave that to the cliche "interested student" -- who also has enough time!

Please note the following:

  • The script is placed in the HTML BODY, not the HEAD. You can place the LED sign almost anywhere you want it to appear, though I found it did not work when nested in a TABLE (maybe I made a mistake or maybe this is some bug or feature lurking in the JavaScript code -- I dunno).
  • The width of the display panel is calculated in the script, based on the length of the longest message line.
  • Messages are easily added and deleted in the script, with no upper limit. They must contain defined characters, which means no upper case. If you use upper case you will get a JavaScript error when it comes to display that letter. If in doubt as to the defined characters, study the script. Messages are stored in a straight-forward fashion at the top of the script, with message numering starting with zero. This example has four messages. To add a fifth, you would add the line:
      messages[4]="yadda, yadda, yadda."
  • The delay between messages is currently set to 3000 milliseconds (3 seconds) in the line:
      var pause = 3000
  • To support the script you need two GIF files, one for the background color ("LED-off.gif") and one for the character symbols ("LED-on.gif"), which are now set respecitvely to black and green. To change either color you would need to replace the file with a graphic of the same size. You could also change the names of these files as long as you similarly change the two script lines where they are defined.
  • Notice that Popeney did a nice thing in designing this to give the page viewer control over the start and stop of the display scrolling. However, if you wanted the scrolling to start automatically whenever the page loads, you could delete the line at the end of the script that contains "onClick="startSign()" and modify the BODY tag:
      <BODY BGCOLOR="#FFFFFF" onLoad="startSign()">