[Javascript] The Fastest Conditionals

The three techniques presented here—the if statement, the switch statement, and array lookup—each have their uses in optimizing code execution:

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.

source: http://archive.oreilly.com/pub/a/server-administration/excerpts/even-faster-websites/writing-efficient-javascript.html#the_fastest_conditionals