The following is a changelog for JavaScript 1.8.1. This version was included in Firefox 3.5.

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.

New features in JavaScript 1.8.1

• Object.getPrototypeOf()
• Support for native JSON
• String.prototype.trim()
• String.prototype.trimLeft()
• String.prototype.trimRight()

Changed functionality in JavaScript 1.8.1

• 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.