Each editor running on the page for a textarea is called an instance. Editor instances have their own variables
and methods that make it easy to edit textarea content. Active instance on the page can be accessed by the
variable "editor.active".(BUE.active in 6.x)

A js button script is executed in a function with the argument E that refers to editor.active.
Here are the VARIABLES of the istance E:

E.index: index of the instance in the array BUE.instances
E.textArea: textarea of the instance as an HTML object.
E.buttons: indexed array of buttons of the instance as HTML objects(input objects, type is button or image)
E.bindex: latest/currently clicked button index that can be used in E.buttons. Ex: E.buttons[E.bindex]
E.tpl(6.x): editor template that this instance uses.(one of BUE.templates)
E.UI(6.x): html object that wraps the instance interface. ()

Here are the METHODS of the instance E:

E.focus():
Focus on the textarea of the instance.

E.getContent():
Returns the content of the textarea.

E.setContent(text):
Replaces the content of the textarea with the given text.

E.getSelection():
Returns the selected text in the textarea.

E.replaceSelection(text, cursor):
Replace the selected text in the textrea with the given text.
The optinal second argument specifies the position of the caret after replacement.
if cursor='start', it is placed at the begining of the replaced text.
if cursor='end', it is placed at the end of the replaced text.
if cursor is not defined, the selection is preserved containing the replaced text.

E.tagSelection(left, right, cursor):
Encloses the selected text in the textarea with the given left and right texts.
The optional third argument specifies the position of the caret after enclosing.
if cursor='start', it is placed at the begining of the selected text.
if cursor='end', it is placed at the end of the selected text.
if cursor is not defined, the selection is preserved.

E.makeSelection(start, end):
Create a selection by selecting the characters between the indexes "start" and "end".

E.posSelection():
Returns the index values of selection start and selection end.
Returns {start: X, end: Y} where X is the start index and Y is the end index.
Note: No selection is also a selection where start=end=caret position.

E.buttonsDisabled(state, bindex):
Dynamically enable/disable buttons of the instance.
the first argument defines the state of the buttons and should be set to true or false.
the optional second argument defines the index of the button whose state will not change.
Ex: to disable all buttons except the pressed button;
js: E.buttonsDisabled(true, E.bindex);