mirrors/ladybird
0
0
Fork 0
mirror of https://github.com/LadybirdBrowser/ladybird.git synced 2025-09-09 19:16:02 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 13

LibJS: Optimize & Bring String.prototype.repeat closer to the spec

Browse source 
Specifically, we immediately return an empty string when `this` is an
empty string, instead of wasting time in a loop doing nothing N times.
This commit is contained in:
Idan Horowitz 2021-06-30 15:19:38 +03:00 • committed by Linus Groh
commit 7d055dd039
Notes: sideshowbarker 2024-07-18 11:12:52 +09:00
1 changed files with 15 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

21
Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
View file

@ -167,21 +167,30 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::repeat)
auto string = ak_string_from(vm, global_object); auto string = ak_string_from(vm, global_object);
if (!string.has_value()) if (!string.has_value())
return {}; return {};
if (!vm.argument_count())
return js_string(vm, String::empty()); auto n = vm.argument(0).to_integer_or_infinity(global_object);
auto count = vm.argument(0).to_integer_or_infinity(global_object);
if (vm.exception()) if (vm.exception())
return {}; return {};
if (count < 0) {
if (n < 0) {
vm.throw_exception<RangeError>(global_object, ErrorType::StringRepeatCountMustBe, "positive"); vm.throw_exception<RangeError>(global_object, ErrorType::StringRepeatCountMustBe, "positive");
return {}; return {};
} }
if (Value(count).is_infinity()) {
if (Value(n).is_positive_infinity()) {
vm.throw_exception<RangeError>(global_object, ErrorType::StringRepeatCountMustBe, "finite"); vm.throw_exception<RangeError>(global_object, ErrorType::StringRepeatCountMustBe, "finite");
return {}; return {};
} }
if (n == 0)
return js_string(vm, String::empty());
// NOTE: This is an optimization, it is not required by the specification but it produces equivalent behaviour
if (string->is_empty())
return js_string(vm, String::empty());
StringBuilder builder; StringBuilder builder;
for (size_t i = 0; i < count; ++i) for (size_t i = 0; i < n; ++i)
builder.append(*string); builder.append(*string);
return js_string(vm, builder.to_string()); return js_string(vm, builder.to_string());
} }