JavaScriptCore wrapper; doesn't work, but could serve as a starting point for something that does.

JavaScriptCore.cs

using System;
using System.Runtime.InteropServices;

using JSObject = WebKit.JSValue;
using JSGlobalContext = WebKit.JSContext;

namespace WebKit {
    #region JSBase.h
    public unsafe struct JSContextGroup { }

    public unsafe struct JSContext { }

    public unsafe struct JSString { }

    public unsafe struct JSClass { }

    public unsafe struct JSPropertyNameArray { }

    public unsafe struct JSPropertyNameAccumulator { }

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate void JSTypedArrayBytesDeallocator(IntPtr bytes, IntPtr deallocatorContext);

    public unsafe struct JSValue { }

    [StructLayout(LayoutKind.Sequential)]
    public unsafe struct JSValueRef {
        public IntPtr p;

        public static implicit operator JSValueRef(JSValue* v) {
            return new JSValueRef { p = (IntPtr)v };
        }

        public static implicit operator JSValue*(JSValueRef r) {
            return (JSValue*)r.p;
        }
    }
    #endregion

    #region JSObjectRef.h
    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate void JSObjectInitializeCallback(JSContext* ctx, JSObject* @object);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate void JSObjectFinalizeCallback(JSObject* @object);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate bool JSObjectHasPropertyCallback(JSContext* ctx, JSObject* @object, JSString* propertyName);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate JSValue* JSObjectGetPropertyCallback(JSContext* ctx, JSObject* @object, JSString* propertyName, JSValue** exception);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate bool JSObjectSetPropertyCallback(JSContext* ctx, JSObject* @object, JSString* propertyName, JSValue* value, JSValue** exception);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate bool JSObjectDeletePropertyCallback(JSContext* ctx, JSObject* @object, JSString* propertyName, JSValue** exception);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate void JSObjectGetPropertyNamesCallback(JSContext* ctx, JSObject* @object, JSPropertyNameAccumulator* propertyNames);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate JSValue* JSObjectCallAsFunctionCallback(JSContext* ctx, JSObject* function, JSObject* thisObject, ulong argumentCount, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] JSValue*[] arguments, JSValue** exception);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate JSObject* JSObjectCallAsConstructorCallback(JSContext* ctx, JSObject* constructor, ulong argumentCount, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)] JSValue*[] arguments, JSValue** exception);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate bool JSObjectHasInstanceCallback(JSContext* ctx, JSObject* constructor, JSValue* possibleInstance, JSValue** exception);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public unsafe delegate JSValue* JSObjectConvertToTypeCallback(JSContext* ctx, JSObject* @object, JSType type, JSValue** exception);

    [StructLayout(LayoutKind.Sequential)]
    public class JSStaticValue {
        [MarshalAs(UnmanagedType.LPStr)]
        public string name;
        public JSObjectGetPropertyCallback getProperty;
        public JSObjectSetPropertyCallback setProperty;
        public uint attributes;
    }

    [StructLayout(LayoutKind.Sequential)]
    public class JSStaticFunction {
        [MarshalAs(UnmanagedType.LPStr)]
        public string name;
        public JSObjectCallAsFunctionCallback callAsFunction;
        public uint attributes;
    }

    [StructLayout(LayoutKind.Sequential)]
    public unsafe class JSClassDefinition {
        public int version; /* current (and only) version is 0 */
        public uint attributes;

        [MarshalAs(UnmanagedType.LPStr)]
        public string className;
        public JSClass* parentClass;

        public JSStaticValue staticValues; // JSStaticValue*
        public JSStaticFunction staticFunctions; // JSStaticFunction*

        public JSObjectInitializeCallback initialize;
        public JSObjectFinalizeCallback finalize;
        public JSObjectHasPropertyCallback hasProperty;
        public JSObjectGetPropertyCallback getProperty;
        public JSObjectSetPropertyCallback setProperty;
        public JSObjectDeletePropertyCallback deleteProperty;
        public JSObjectGetPropertyNamesCallback getPropertyNames;
        public JSObjectCallAsFunctionCallback callAsFunction;
        public JSObjectCallAsConstructorCallback callAsConstructor;
        public JSObjectHasInstanceCallback hasInstance;
        public JSObjectConvertToTypeCallback convertToType;

        public static JSClassDefinition kJSClassDefinitionEmpty {
            get {
                return new JSClassDefinition { /* 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 */ };
            }
        }
    }
    #endregion

    #region JSValueRef.h
    public enum JSType {
        kJSTypeUndefined,
        kJSTypeNull,
        kJSTypeBoolean,
        kJSTypeNumber,
        kJSTypeString,
        kJSTypeObject
    }

    public enum JSTypedArrayType {
        kJSTypedArrayTypeInt8Array,
        kJSTypedArrayTypeInt16Array,
        kJSTypedArrayTypeInt32Array,
        kJSTypedArrayTypeUint8Array,
        kJSTypedArrayTypeUint8ClampedArray,
        kJSTypedArrayTypeUint16Array,
        kJSTypedArrayTypeUint32Array,
        kJSTypedArrayTypeFloat32Array,
        kJSTypedArrayTypeFloat64Array,
        kJSTypedArrayTypeArrayBuffer,
        kJSTypedArrayTypeNone,
    }
    #endregion

    public unsafe static class JavaScriptCore {
#if UNITY_IPHONE && !UNITY_EDITOR
        private const string PLATFORM_DLL = "__Internal";
#else
        private const string PLATFORM_DLL = "JavaScriptCore";
#endif

        #region JSBase.h
        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSEvaluateScript(JSContext* ctx, JSString* script, JSObject* thisObject, JSString* sourceURL, int startingLineNumber, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSCheckScriptSyntax(JSContext* ctx, JSString* script, JSString* sourceURL, int startingLineNumber, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSGarbageCollect(JSContext* ctx);
        #endregion

        #region JSContextRef.h
        [DllImport(PLATFORM_DLL)]
        public static extern JSContextGroup* JSContextGroupCreate();

        [DllImport(PLATFORM_DLL)]
        public static extern JSContextGroup* JSContextGroupRetain(JSContextGroup* group);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSContextGroupRelease(JSContextGroup* group);

        [DllImport(PLATFORM_DLL)]
        public static extern JSGlobalContext* JSGlobalContextCreate(JSClass* globalObjectClass);

        [DllImport(PLATFORM_DLL)]
        public static extern JSGlobalContext* JSGlobalContextCreateInGroup(JSContextGroup* group, JSClass* globalObjectClass);

        [DllImport(PLATFORM_DLL)]
        public static extern JSGlobalContext* JSGlobalContextRetain(JSGlobalContext* ctx);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSGlobalContextRelease(JSGlobalContext* ctx);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSContextGetGlobalObject(JSContext* ctx);

        [DllImport(PLATFORM_DLL)]
        public static extern JSContextGroup* JSContextGetGroup(JSContext* ctx);

        [DllImport(PLATFORM_DLL)]
        public static extern JSGlobalContext* JSContextGetGlobalContext(JSContext* ctx);

        [DllImport(PLATFORM_DLL)]
        public static extern JSString* JSGlobalContextCopyName(JSGlobalContext* ctx);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSGlobalContextSetName(JSGlobalContext* ctx, JSString* name);
        #endregion

        #region JSObjectRef.h
        [DllImport(PLATFORM_DLL)]
        public static extern JSClass* JSClassCreate(JSClassDefinition definition);

        [DllImport(PLATFORM_DLL)]
        public static extern JSClass* JSClassRetain(JSClass* jsClass);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSClassRelease(JSClass* jsClass);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectMake(JSContext* ctx, JSClass* jsClass, IntPtr data);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectMakeFunctionWithCallback(JSContext* ctx, JSString* name, JSObjectCallAsFunctionCallback callAsFunction);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectMakeConstructor(JSContext* ctx, JSClass* jsClass, JSObjectCallAsConstructorCallback callAsConstructor);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectMakeArray(JSContext* ctx, ulong argumentCount, JSValue*[] arguments, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectMakeDate(JSContext* ctx, ulong argumentCount, JSValue*[] arguments, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectMakeError(JSContext* ctx, ulong argumentCount, JSValue*[] arguments, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectMakeRegExp(JSContext* ctx, ulong argumentCount, JSValue*[] arguments, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectMakeFunction(JSContext* ctx, JSString* name, uint parameterCount, JSString*[] parameterNames, JSString* body, JSString* sourceURL, int startingLineNumber, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSObjectGetPrototype(JSContext* ctx, JSObject* @object);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSObjectSetPrototype(JSContext* ctx, JSObject* @object, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSObjectHasProperty(JSContext* ctx, JSObject* @object, JSString* propertyName);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSObjectGetProperty(JSContext* ctx, JSObject* @object, JSString* propertyName, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSObjectSetProperty(JSContext* ctx, JSObject* @object, JSString* propertyName, JSValue* value, uint attributes, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSObjectDeleteProperty(JSContext* ctx, JSObject* @object, JSString* propertyName, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSObjectGetPropertyAtIndex(JSContext* ctx, JSObject* @object, uint propertyIndex, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSObjectSetPropertyAtIndex(JSContext* ctx, JSObject* @object, uint propertyIndex, JSValue* value, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern IntPtr JSObjectGetPrivate(JSObject* @object);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSObjectSetPrivate(JSObject* @object, IntPtr data);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSObjectIsFunction(JSContext* ctx, JSObject* @object);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSObjectCallAsFunction(JSContext* ctx, JSObject* @object, JSObject* thisObject, ulong argumentCount, JSValue*[] arguments, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSObjectIsConstructor(JSContext* ctx, JSObject* @object);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSObjectCallAsConstructor(JSContext* ctx, JSObject* @object, ulong argumentCount, JSValue*[] arguments, [Out] JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSPropertyNameArray* JSObjectCopyPropertyNames(JSContext* ctx, JSObject* @object);

        [DllImport(PLATFORM_DLL)]
        public static extern JSPropertyNameArray* JSPropertyNameArrayRetain(JSPropertyNameArray* array);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSPropertyNameArrayRelease(JSPropertyNameArray* array);

        [DllImport(PLATFORM_DLL)]
        public static extern ulong JSPropertyNameArrayGetCount(JSPropertyNameArray* array);

        [DllImport(PLATFORM_DLL)]
        public static extern JSString* JSPropertyNameArrayGetNameAtIndex(JSPropertyNameArray* array, ulong index);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSPropertyNameAccumulatorAddName(JSPropertyNameAccumulator* accumulator, JSString* propertyName);
        #endregion

        #region JSStringRef.h
        [DllImport(PLATFORM_DLL)]
        public static extern JSString* JSStringCreateWithCharacters(ushort[] chars, ulong numChars);
        
        [DllImport(PLATFORM_DLL)]
        public static extern JSString* JSStringCreateWithUTF8CString(byte[] @string);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSStringRelease(JSString* @string);

        [DllImport(PLATFORM_DLL)]
        public static extern JSString* JSStringRetain(JSString* @string);

        [DllImport(PLATFORM_DLL)]
        public static extern ushort[] JSStringGetCharactersPtr(JSString* @string);

        [DllImport(PLATFORM_DLL)]
        public static extern ulong JSStringGetLength(JSString* @string);

        [DllImport(PLATFORM_DLL)]
        public static extern ulong JSStringGetMaximumUTF8CStringSize(JSString* @string);

        [DllImport(PLATFORM_DLL)]
        public static extern ulong JSStringGetUTF8CString(JSString* @string, byte[] buffer, ulong bufferSize);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSStringIsEqual(JSString* a, JSString* b);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSStringIsEqualToUTF8CString(JSString* a, byte[] b);
        #endregion

        #region JSValueRef.h
        [DllImport(PLATFORM_DLL)]
        public static extern JSType JSValueGetType(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsUndefined(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsNull(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsBoolean(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsNumber(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsString(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsObject(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsObjectOfClass(JSContext* ctx, JSValue* value, JSClass* jsClass);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsArray(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsDate(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern JSTypedArrayType JSValueGetTypedArrayType(JSContext* ctx, JSValue* value, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsEqual(JSContext* ctx, JSValue* a, JSValue* b, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsStrictEqual(JSContext* ctx, JSValue* a, JSValue* b);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueIsInstanceOfConstructor(JSContext* ctx, JSValue* value, JSObject* constructor, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSValueMakeUndefined(JSContext* ctx);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSValueMakeNull(JSContext* ctx);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSValueMakeBoolean(JSContext* ctx, bool boolean);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSValueMakeNumber(JSContext* ctx, double number);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSValueMakeString(JSContext* ctx, JSString* @string);

        [DllImport(PLATFORM_DLL)]
        public static extern JSValue* JSValueMakeFromJSONString(JSContext* ctx, JSString* @string);

        [DllImport(PLATFORM_DLL)]
        public static extern JSString* JSValueCreateJSONString(JSContext* ctx, JSValue* value, uint indent, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern bool JSValueToBoolean(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern double JSValueToNumber(JSContext* ctx, JSValue* value, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSString* JSValueToStringCopy(JSContext* ctx, JSValue* value, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern JSObject* JSValueToObject(JSContext* ctx, JSValue* value, JSValue** exception);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSValueProtect(JSContext* ctx, JSValue* value);

        [DllImport(PLATFORM_DLL)]
        public static extern void JSValueUnprotect(JSContext* ctx, JSValue* value);
        #endregion
    }
}