User Agent: Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.63 Safari/537.31 Steps to reproduce: http://jsperf.com/array-memory-access-optimization I'm changing the view on a 3D grid by swapping values around. My focus was in comparing between Chrome and Firefox performance more than comparing the performance difference between the two tests shown on jsperf. Actual results: Firefox is anywhere between 10-20 times slower than Chrome for the same tests Expected results: Would have expected a smaller performance gap between the two browsers.

Firefox Nightly is a lot faster for me than Chrome 26: Browser FF Chrome Writing 38.66 16.37 Reading 48.85 30.06

Pretty sure this is bug 827490 (should be fixed in Firefox 21, will be released next week). Simple workaround is to use [] instead of {} here: var axial_view = {}; and here: var sagittal_view = {};