JavaScript : Copy text to the clipboard, without Flash and securely (Updated!)

Github (Alexa: #348), Kickstarter (Alexa: #774), and many other major web-sites are increasingly using a flash-based button to facilitate one-click-copying of text, an otherwise disallowed action. Put aptly, by several stackoverflow-users, this method is 'overkill'. Basically a translucent flash applet is overlayed on a button-graphic to perform a clipboard-copying action, upon clicking the applet. Questionable security behavior is thus proxied to the flash applet, as the post-flash era draws near. Some browsers support document.execCommand('copy') ,which allows placing content, marked editable, into the Clipboard. However, the methodology dates back to the IE-5 era, which is more than a decade past, and execCommand is only loosely supported, yielding mixed results.
Jarek Milewski provides a better solution , which can be seen in action here.
By invoking a dialog-prompt as follows, window.prompt('Dialog text', refvariable); , a native-UI modal-input dialog is shown, with preselected text. The user is then offered the choice to click CTRL+C and hit ENTER.

Find the Source-Code on Gist, or below:

Click on the file-path below to copy and paste the selected text into the file-dialog below, thus allowing quick navigation to a specific file.

► Implementation #1 ( window -prompt):

► Implementation #2 (preselected textbox):

► Implementation #3 (direct textbox):

► Implementation #3 ( using an input -tag set to readonly; inspired by ):


Copying cannot be straightforward, as the Browser is obliged to uphold an encapsulated, sandboxed environment, with many security considerations at play. Prompting the user before performing a clipboard action, offers currently the best measure which is effective whilst less obtrusive than other methods. Given the increasing spreading of flash-based clipboard copying, the issue should not be neglected and alternative fully HTML5 / DOM compliant methods should be pursued.

Extension (Forward a user to a site upon successful copying):

Alyce C asked me
I wonder if there's also a way to add more script to this which, after copying to clipboard, will forward the website visitor to another URL. Thanks!

The answer is Yes. At this point it should be stated that for obvious reasons of data security and user privacy, a protection of reading and writing clipboard-data is in place. Otherwise it would be easy to track a user via Browser-Ids and collect sensitive user data such as passwords over time as a user visits a site.
This is not a problem however, as all that is required to forward a user upon successfully copy-and-pasting the content in question is listening to the keyboard events containing the keys CTRL+C to subsequently forward the user to the location. (For more on keyboard events see keyBoarder and this Keytable):