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LibJS: Add StringPrototype and make it the prototype of StringObject

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This patch adds String.prototype.charAt() to demonstrate that prototype
property lookup works, and that you can call a prototype function on an
object, and it will do what you expect. :^)
This commit is contained in:
Andreas Kling 2020-03-15 15:02:49 +01:00
parent f7c15d00c9
commit 2c5b9fb8f9
6 changed files with 109 additions and 0 deletions
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57
Libraries/LibJS/StringPrototype.cpp Normal file
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/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/Function.h>
#include <LibJS/Heap.h>
#include <LibJS/Interpreter.h>
#include <LibJS/PrimitiveString.h>
#include <LibJS/StringObject.h>
#include <LibJS/StringPrototype.h>
#include <LibJS/Value.h>
namespace JS {
StringPrototype::StringPrototype()
{
put_native_function("charAt", [](Interpreter& interpreter, Vector<Value> arguments) -> Value {
i32 index = 0;
if (!arguments.is_empty())
index = arguments[0].to_i32();
Value this_value = interpreter.this_value();
ASSERT(this_value.is_object());
ASSERT(this_value.as_object()->is_string_object());
auto underlying_string = static_cast<const StringObject*>(this_value.as_object())->primitive_string()->string();
if (index < 0 || index >= static_cast<i32>(underlying_string.length()))
return js_string(interpreter.heap(), String::empty());
return js_string(interpreter.heap(), underlying_string.substring(index, 1));
});
}
StringPrototype::~StringPrototype()
{
}
}