New in JavaScript 1.8.1

Introduced in Gecko 1.9.1

(Firefox 3.5 / Thunderbird 3 / SeaMonkey 2)

JavaScript 1.8.1 is a modest update syntactically to JavaScript; the main change in this release is the addition of the  Tracemonkey just-in-time compiler , which improves performance.

There is a notable API change removing the branch callback and replacing the operation callback  detailed in this newsgroup posting .

Language additions

Object.getPrototypeOf()

This new method returns the prototype of a specified object.

Using native JSON

Firefox 3.5 has native support for   JSON .

New trim methods on the String object

The   String   object now has   trim() ,   trimLeft() , and   trimRight()  methods.

Other improvements

• Implicit setting of properties in object and array initializers no longer execute setters in JavaScript. This makes the behavior of setting the values of properties more predictable. See the blog post  Object and array initializers should not invoke setters when evaluated   for details.