LibJS: Add String.fromCharCode()

Libraries/LibJS/Runtime/StringConstructor.cpp

@@ -25,6 +25,7 @@
  */
 
 #include <AK/StringBuilder.h>
+#include <AK/Utf32View.h>
 #include <LibJS/Interpreter.h>
 #include <LibJS/Runtime/Array.h>
 #include <LibJS/Runtime/Error.h>
@@ -40,7 +41,9 @@ StringConstructor::StringConstructor()
     define_property("prototype", interpreter().global_object().string_prototype(), 0);
     define_property("length", Value(1), Attribute::Configurable);
 
-    define_native_function("raw", raw, 0, Attribute::Writable | Attribute::Configurable);
+    u8 attr = Attribute::Writable | Attribute::Configurable;
+    define_native_function("raw", raw, 0, attr);
+    define_native_function("fromCharCode", from_char_code, 1, attr);
 }
 
 StringConstructor::~StringConstructor()
@@ -106,4 +109,18 @@ Value StringConstructor::raw(Interpreter& interpreter)
     return js_string(interpreter, builder.build());
 }
 
+Value StringConstructor::from_char_code(Interpreter& interpreter)
+{
+    StringBuilder builder;
+    for (size_t i = 0; i < interpreter.argument_count(); ++i) {
+        auto char_code = interpreter.argument(i).to_i32(interpreter);
+        if (interpreter.exception())
+            return {};
+        auto truncated = char_code & 0xffff;
+        // FIXME: We need an Utf16View :^)
+        builder.append(Utf32View((u32*)&truncated, 1));
+    }
+    return js_string(interpreter, builder.build());
+}
+
 }

Libraries/LibJS/Runtime/StringConstructor.h

@@ -43,6 +43,7 @@ private:
     virtual const char* class_name() const override { return "StringConstructor"; }
 
     static Value raw(Interpreter&);
+    static Value from_char_code(Interpreter&);
 };
 
 }

Libraries/LibJS/Tests/String.fromCharCode.js

@@ -0,0 +1,23 @@
+load("test-common.js");
+
+try {
+    assert(String.fromCharCode.length === 1);
+    
+    assert(String.fromCharCode() === "");
+    assert(String.fromCharCode(0) === "\u0000");
+    assert(String.fromCharCode(false) === "\u0000");
+    assert(String.fromCharCode(null) === "\u0000");
+    assert(String.fromCharCode(undefined) === "\u0000");
+    assert(String.fromCharCode(1) === "\u0001");
+    assert(String.fromCharCode(true) === "\u0001");
+    assert(String.fromCharCode(-1) === "\uffff");
+    assert(String.fromCharCode(0xffff) === "\uffff");
+    assert(String.fromCharCode(0x123ffff) === "\uffff");
+    assert(String.fromCharCode(65) === "A");
+    assert(String.fromCharCode(65, 66, 67) === "ABC");
+    assert(String.fromCharCode(228, 246, 252) === "äöü");
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}