Lookup table for result matching

When optimizing if/else, minimize the number of conditions to evaluate. This applies to switch cases as well.

The easiest optimization is to ensure that the most common conditions are first:

if (value < 5) {
  // most frequent case
} else if (value > 5 && value < 10) {
  // second most frequent case
} else {
 // other less frequent cases

Index lookups

It’s sometimes better to use a direct match approach using object/array index lookups:

var lookupTable = {
  '1': 'is greater',
  '-1': 'is less',
  '0': 'is equal'

var myValue = 5

lookupTable[compare(4, myValue)]

In objects, you may also use falsy values as keys.

Array vs. Object

Be careful about choosing between Object or Array:

  • If you need a incremental index, use Array.
  • In other cases, use Object.


Although it is more readable, using a lookup table isn’t always better. The cost of creating the lookup table could be higher than using a set of if/else statements. So, it depends on your code:

  • If you have to handle a small set of conditions (maybe less than 3) or the code runtime life is short, use if/else.
  • In other cases, use a lookup table.