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

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This commit is contained in:
Timothy Flynn 2021-07-19 11:13:39 -04:00 • committed by Andreas Kling
parent 2bba20d123
commit 5d11614bc7
2 changed files with 24 additions and 4 deletions
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20
Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
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@ -8,6 +8,7 @@
#include <AK/Checked.h>
#include <AK/Function.h>
#include <AK/StringBuilder.h>
#include <AK/Utf16View.h>
#include <LibJS/Heap/Heap.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Array.h>
@ -31,6 +32,14 @@ static Optional<String> ak_string_from(VM& vm, GlobalObject& global_object)
return this_value.to_string(global_object);
}
static Vector<u16> utf16_string_from(VM& vm, GlobalObject& global_object)
{
auto this_value = require_object_coercible(global_object, vm.this_value(global_object));
if (vm.exception())
return {};
return this_value.to_utf16_string(global_object);
}
static Optional<size_t> split_match(const String& haystack, size_t start, const String& needle)
{
auto r = needle.length();
@ -119,15 +128,18 @@ static Value this_string_value(GlobalObject& global_object, Value value)
// 22.1.3.1 String.prototype.charAt ( pos ), https://tc39.es/ecma262/#sec-string.prototype.charat
JS_DEFINE_NATIVE_FUNCTION(StringPrototype::char_at)
{
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 position = vm.argument(0).to_integer_or_infinity(global_object);
if (vm.exception())
return {};
if (position < 0 || position >= string->length())
Utf16View utf16_string_view { string };
if (position < 0 || position >= utf16_string_view.length_in_code_units())
return js_string(vm, String::empty());
return js_string(vm, string->substring(position, 1));
return js_string(vm, utf16_string_view.substring_view(position, 1));
}
// 22.1.3.2 String.prototype.charCodeAt ( pos ), https://tc39.es/ecma262/#sec-string.prototype.charcodeat

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

@ -18,3 +18,11 @@ test("basic functionality", () => {
expect(s.charAt("foo")).toBe("f");
expect(s.charAt(undefined)).toBe("f");
});
test("UTF-16", () => {
var s = "😀";
expect(s).toHaveLength(2);
expect(s.charAt(0)).toBe("\ud83d");
expect(s.charAt(1)).toBe("\ude00");
expect(s.charAt(2)).toBe("");
});