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

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Timothy Flynn 2021-07-19 13:34:41 -04:00 committed by Andreas Kling
parent 60d8852fc2
commit 892bfdbbcf
Notes: sideshowbarker 2024-07-18 08:35:45 +09:00 
Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/892bfdbbcf1
Pull-request: https://github.com/SerenityOS/serenity/pull/8897
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/davidot
2 changed files with 18 additions and 10 deletions
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17
Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
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@ -527,14 +527,12 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::substring)
// B.2.3.1 String.prototype.substr ( start, length ), https://tc39.es/ecma262/#sec-string.prototype.substr
JS_DEFINE_NATIVE_FUNCTION(StringPrototype::substr)
{
auto string = ak_string_from(vm, global_object);
if (!string.has_value())
auto string = utf16_string_from(vm, global_object);
if (vm.exception())
return {};
if (vm.argument_count() == 0)
return js_string(vm, *string);
// FIXME: this should index a UTF-16 code_point view of the string.
auto size = (i32)string->length();
Utf16View utf16_string_view { string };
auto size = utf16_string_view.length_in_code_units();
auto int_start = vm.argument(0).to_integer_or_infinity(global_object);
if (vm.exception())
@ -551,15 +549,14 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::substr)
return {};
if (Value(int_start).is_positive_infinity() || (int_length <= 0) || Value(int_length).is_positive_infinity())
return js_string(vm, String(""));
return js_string(vm, String::empty());
auto int_end = min((i32)(int_start + int_length), size);
if (int_start >= int_end)
return js_string(vm, String(""));
return js_string(vm, String::empty());
auto string_part = string->substring(int_start, int_end - int_start);
return js_string(vm, string_part);
return js_string(vm, utf16_string_view.substring_view(int_start, int_end - int_start));
}
// 22.1.3.7 String.prototype.includes ( searchString [ , position ] ), https://tc39.es/ecma262/#sec-string.prototype.includes

11
Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.substr.js
View file

@ -17,3 +17,14 @@ test("basic functionality", () => {
expect("hello friends".substr(-7)).toBe("friends");
expect("hello friends".substr(-3, -5)).toBe("");
});
test("UTF-16", () => {
var s = "😀";
expect(s).toHaveLength(2);
expect(s.substr()).toBe("😀");
expect(s.substr(0)).toBe("😀");
expect(s.substr(0, 2)).toBe("😀");
expect(s.substr(0, 1)).toBe("\ud83d");
expect(s.substr(1, 1)).toBe("\ude00");
expect(s.substr(2, 1)).toBe("");
});