为什么数组。有时推得比数组[n] =值快?

As a side result of testing some code I wrote a small function to compare the speed of using the array.push method vs direct addressing (array[n] = value). To my surprise the push method often showed to be faster especially in Firefox and sometimes in Chrome. Just out of curiosity: anyone has an explanation for it? You can find the test @As a side result of testing some code I wrote a