Select (highlight) All Javascript

To ease your work, I decided to equip my code boxes with a 'Select All' function, so that you can easily highlight the text in the box, copy it and paste it into your .html file. I searched a lot and the only one that really worked for me and was very simple was the forum thread called Select All Text In A Form Field On Click. You can test this by clicking into any of the code boxes I posted.