Square brackets: in documentation, optional arguments

In documentation of code, as opposed to code itself, the common technical writing convention is followed whereby something used optionally, i.e. that which may be omitted, is placed inside [ ] brackets. In this case the [ ] are not part of the syntax used in code, but they simply indicate the optional omissions

An obvious place to see examples of this is in aTbRef's full list of operators.

As an example, the if() conditional test:

if(condition){...actions...}[else{...actions...}] 

Note the second part starting else is inside [ ] square brackets. This implies that both these are valid syntax:

if(condition){...actions...}else{...actions...}; 

or

if(condition){...actions...};