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LibJS: Implement String.prototype.startsWith with UTF-16 code units

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This commit is contained in:
Timothy Flynn 2021-07-19 15:57:05 -04:00 • committed by Andreas Kling
parent f920e121b3
commit d2e63a641f
2 changed files with 26 additions and 9 deletions
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27
Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
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@ -258,8 +258,8 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::repeat)
// 22.1.3.22 String.prototype.startsWith ( searchString [ , position ] ), https://tc39.es/ecma262/#sec-string.prototype.startswith
JS_DEFINE_NATIVE_FUNCTION(StringPrototype::starts_with)
{
auto string = ak_string_from(vm, global_object);
if (!string.has_value())
auto string = utf16_string_from(vm, global_object);
if (vm.exception())
return {};
auto search_string_value = vm.argument(0);
@ -272,12 +272,16 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::starts_with)
return {};
}
auto search_string = search_string_value.to_string(global_object);
auto search_string = search_string_value.to_utf16_string(global_object);
if (vm.exception())
return {};
auto string_length = string->length();
auto search_string_length = search_string.length();
Utf16View utf16_string_view { string };
auto string_length = utf16_string_view.length_in_code_units();
Utf16View utf16_search_view { search_string };
auto search_length = utf16_search_view.length_in_code_units();
size_t start = 0;
if (!vm.argument(1).is_undefined()) {
auto position = vm.argument(1).to_integer_or_infinity(global_object);
@ -285,11 +289,16 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::starts_with)
return {};
start = clamp(position, static_cast<double>(0), static_cast<double>(string_length));
}
if (start + search_string_length > string_length)
return Value(false);
if (search_string_length == 0)
if (search_length == 0)
return Value(true);
return Value(string->substring(start, search_string_length) == search_string);
size_t end = start + search_length;
if (end > string_length)
return Value(false);
utf16_string_view = utf16_string_view.substring_view(start, end - start);
return Value(utf16_string_view == utf16_search_view);
}
// 22.1.3.6 String.prototype.endsWith ( searchString [ , endPosition ] ), https://tc39.es/ecma262/#sec-string.prototype.endswith

8
Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.startsWith.js
View file

@ -34,3 +34,11 @@ test("basic functionality", () => {
expect(s.startsWith("", -1)).toBeTrue();
expect(s.startsWith("", 42)).toBeTrue();
});
test("UTF-16", () => {
var s = "😀";
expect(s.startsWith("😀")).toBeTrue();
expect(s.startsWith("\ud83d")).toBeTrue();
expect(s.startsWith("\ude00")).toBeFalse();
expect(s.startsWith("a")).toBeFalse();
});