+ eval("x + 2")); ... })(); val 9 undefined See also Comparison of JavaScript-based source code editors JavaScript References Further reading Danny Goodman: JavaScript Bible, Wiley, John & Sons, . David Flanagan, Paula Ferguson: JavaScript: The Definitive Guide, O'Reilly & Associates, . Thomas A. Powell, Fritz Schneider: JavaScript: The Complete Reference, McGraw-Hill Companies, . Axel Rauschmayer: Speaking JavaScript: An In-Depth Guide for Programmers, 460 pages, O'Reilly Media, 25 February 2014, . (free online edition) Emily Vander Veer: JavaScript For Dummies, 4th Edition, Wiley, . External links A re-introduction to JavaScript - Mozilla Developer Center JavaScript Loops ECMAScript standard references: ECMA-262 Interactive JavaScript Lessons - example-based JavaScript on About.com: lessons and explanation JavaScript Training Mozilla Developer Center Core References for JavaScript versions 1.5, 1.4, 1.3 and 1.2 Mozilla JavaScript Language Documentation syntax Programming language syntax