“Even Faster Websites”

OReily Even Faster Websites is a great book. It has some Javascript perfomance hints in its “Writing Efficient JavaScript” part. Here are conclusions:

• Use local variables
• Avoid with statement
• do not use too deep properies, redefine them with locals if possible
• Use the if statement when:
  — There are no more than two discrete values for which to test.
  — There are a large number of values that can be easily separated into ranges.
• Use the switch statement when:
  — There are more than two but fewer than 10 discrete values for which to test.
  — There are no ranges for conditions because the values are nonlinear.
• Use array lookup when:
  — There are more than 10 values for which to test.
  — The results of the conditions are single values rather than a number of actions
  to be taken.
• To improve perfomance of loops decrement the iterator toward 0 rather than incrementing toward the total length.