src/v8/test/intl/overrides/caching.js

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// Performance test for overriden methods. Makes sure that default case
// is faster (cached) than the general case.

// Default, cached.
var startTime = new Date();
for (var i = 0; i < 1000; i++) {
  'a'.localeCompare('c');
}
var endTime = new Date();
var cachedTime = endTime.getTime() - startTime.getTime();

// Not cached.
startTime = new Date();
for (var i = 0; i < 1000; i++) {
  'a'.localeCompare('c', 'sr');
}
endTime = new Date();
var nonCachedTime = endTime.getTime() - startTime.getTime();

// Using collator. Faster than default, but not by much.
var collator = Intl.Collator();
startTime = new Date();
for (var i = 0; i < 1000; i++) {
  collator.compare('a', 'c');
}
endTime = new Date();
collatorTime = endTime.getTime() - startTime.getTime();

// Difference is within 20%.
assertTrue(collatorTime < cachedTime);
// Non-cached time is much slower, measured to 12.5 times.
assertTrue(cachedTime < nonCachedTime);