Is Switch Faster Than a Lookup Table in JavaScript? A 50,000-Iteration Test

In the book “High‑Performance JavaScript” a “lookup table” is recommended as faster than if‑else or switch when many discrete values need to be tested. To verify this claim I wrote two functions – one using a switch statement and another using a lookup table – and measured their execution time over 50 000 iterations.

Switch version (illustrated in the first screenshot):

Lookup‑table version (second screenshot):

The test code used was:

var index = 0;
console.time('test');
for (var i = 50000; i >= 0; i--) {
    index = index == 10 ? 0 : index;
    // simulate a lookup or switch call
    // search(index++);
}
console.timeEnd('test');

Running the test five times produced the following results (in milliseconds):

Switch: 1.25, 0.91, 1.22, 1.31, 0.89

Lookup table: 1.86, 1.43, 3.13, 1.08, 1.05

Contrary to the book’s assertion, the switch implementation was slightly faster on average. The difference, however, is marginal and unlikely to affect overall system performance.

Beyond raw speed, the lookup‑table approach has two clear advantages:

Code clarity : the logic is more straightforward than a long chain of if‑else or switch cases.

Maintainability : adding or removing conditions only requires updating the table, not restructuring control flow.

From this experiment I learned two lessons:

Never rely solely on book recommendations; empirical testing is essential.

Even familiar patterns deserve reconsideration when alternative solutions may offer better readability or maintainability.