1. conception

• Variables in 'FXS' are references to values.
• Variables that are not declared are directly assigned to use and will be defined as global variables.
• If only variables are declared and not assigned, the default value is 'undefined'.
• var behaves in line with JavaScript and will have variable boosts.

var foo = 1;
var bar = "hello world";
var i;  i === undefined

The above code declares the three variables of 'foo', 'bar', and 'i'. Then, 'foo' is assigned the value '1' and 'bar' is assigned to the string ''hello world''.

2. The variable name

Variable naming must conform to the following two rules:

• The first character must be: letter (a-zA-Z), underscore (_)
• The remaining characters can be: letters (a-zA-Z), underscores (_), numbers (0-9)

3. Reserved identifiers

The following identifiers cannot be used as variable names:

delete
void
typeof

null
undefined
NaN
Infinity
var

if
else

true
false

require

this
function
arguments
return

for
while
do
break
continue
switch
case
default