Question

js> (5).toString(2)
101

js> 5.toString(2)  
js: "<stdin>", line 53: missing ; before statement
js: 5.toString(2)
js: ..........^
js> 

Answer 1

Javascript assumes (bizarrely) that a number followed by a dot means the dot is a decimal point. This is counter-intuitive, but at least it’s reliable.

You have several choices as to how you deal with this:

(5).toString(2); #1
5..toString(2);  #2
5.0.toString(2); #3
5 .toString(2);  #4

Stackoverflow’s syntax highlighter shows you that, in #2 and #3, the first dot is considered to be part of the number and the second to be the operator. In #4, we can see that the space tells the parser that the number has ended.