1# Working with Wrapper Objects Using JSVM-API 2 3## Introduction 4 5This topic walks you through on how to use JSVM-API to quickly determine the wrapper object type. 6 7## Basic Concepts 8 9JSVM-API provides APIs for determining five wrapper object types: number, Boolean, BigInt, string, and symbol. 10 11## Available APIs 12 13| API | Description | 14|----------------------------------------|--------------------------------| 15| OH_JSVM_IsNumberObject | Checks whether the result is a number object. | 16| OH_JSVM_IsBooleanObject | Checks whether the result is a Boolean object. | 17| OH_JSVM_IsBigIntObject | Checks whether the result is a BigInt object. | 18| OH_JSVM_IsStringObject | Checks whether the result is a string object. | 19| OH_JSVM_IsSymbolObject | Checks whether the result is a symbol object. | 20 21## Example 22 23If you are just starting out with JSVM-API, see [JSVM-API Development Process](use-jsvm-process.md). The following demonstrates only the C++ code involved in manipulating wrapper objects. 24 25### Determining a Number Object 26 27CPP code: 28 29```cpp 30static JSVM_Value WrapperObject(JSVM_Env env, JSVM_CallbackInfo info) { 31 JSVM_VM vm; 32 OH_JSVM_GetVM(env, &vm); 33 34 JSVM_HandleScope handleScope; 35 OH_JSVM_OpenHandleScope(env, &handleScope); 36 string src = R"JS(new Number(42))JS"; 37 JSVM_Value jsSrc; 38 JSVM_Script script; 39 JSVM_Value result; 40 41 OH_JSVM_CreateStringUtf8(env, src.c_str(), JSVM_AUTO_LENGTH, &jsSrc); 42 OH_JSVM_CompileScript(env, jsSrc, nullptr, 0, true, nullptr, &script); 43 OH_JSVM_RunScript(env, script, &result); 44 bool isNumberObject = false; 45 OH_JSVM_IsNumberObject(env, result, &isNumberObject); 46 OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_IsNumberObject: %{public}d\n", isNumberObject); 47 OH_JSVM_CloseHandleScope(env, handleScope); 48 49 return nullptr; 50} 51 52static JSVM_CallbackStruct param[] = { 53 {.data = nullptr, .callback = WrapperObject}, 54}; 55 56static JSVM_CallbackStruct *method = param; 57 58// Alias for the wrapperObject method to be called from JS. 59static JSVM_PropertyDescriptor descriptor[] = { 60 {"wrapperObject", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT}, 61}; 62 63// Call the C++ code from JS. 64const char *srcCallNative = R"JS(wrapperObject();)JS"; 65 66``` 67 68Expected result: 69``` 70JSVM OH_JSVM_IsNumberObject: 1 71``` 72