Parameter syntax:
[ 'backwards' ]?
If caret is inside a paragraph-like element at any nesting level and if caret is located after the last character of this element, joins this paragraph-like element to the following paragraph-like element of the same type.
If backwards
option is used, if caret is inside a paragraph-like element at any nesting level and if caret is located before the first character of this element, joins this paragraph-like element to the preceding paragraph-like element of the same type
Otherwise works like deleteChar.
A paragraph-like element is any type of element having no required attributes and containing text and possibly child elements but in any order and in any number.