Function declaration speed difference in JS

Question

I ran a simple jsperf test and everything went as expected when running in Firefox but when I ran the test in Google Chrome is was confused.

The test is testing different ways of declaring function in JavaScript and then calling them. My guess is that Chrome is doing some sort of optimization on the JavaScript function but I'm not sure what or why there is such a big difference. Any help or links to understand this better is greatly appreciated.

Link to test => http://jsperf.com/function-assignment-semicolon/2

Test run in Firefox:

Test in Chrome:

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Edit:

I expected the results I got from Firefox because I expected them to be - fairly the same for each test - slower than when run in Google Chrome

Answer 1

Dead code, a perfect optimizer would remove everything in the test. This has been mentioned on various news sites with the recent announcement of Google's Crankshaft engine. The differences between styles are an indication of how difficult it is to implement dead code optimisation.

http://tech.slashdot.org/story/10/12/07/2027259/Google-Quietly-Posts-Big-JavaScript-Engine-Update