12               // The number twelve
1.2              // The number one point two
"hello world"    // A string of text
'Hi'             // Another string
true             // A boolean value
false            // The other boolean value
/javascript/gi   // A "regular expression" literal (for pattern matching)
null             // Absence of an object 

{ x:1, y:2 }    // An object initializer
[1,2,3,4,5]     // An array initializer 

Note that these array and object literals have been supported since JavaScript 1.2 but were not standardized until ECMAScript v3.