harmony 鸿蒙Working with Wrapper Objects Using JSVM-API

2025-06-12
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Working with Wrapper Objects Using JSVM-API

Introduction

This topic walks you through on how to use JSVM-API to quickly determine the wrapper object type.

Basic Concepts

JSVM-API provides APIs for determining five wrapper object types: number, Boolean, BigInt, string, and symbol.

Available APIs

API	Description
OH_JSVM_IsNumberObject	Checks whether the result is a number object.
OH_JSVM_IsBooleanObject	Checks whether the result is a Boolean object.
OH_JSVM_IsBigIntObject	Checks whether the result is a BigInt object.
OH_JSVM_IsStringObject	Checks whether the result is a string object.
OH_JSVM_IsSymbolObject	Checks whether the result is a symbol object.

Example

If you are just starting out with JSVM-API, see JSVM-API Development Process. The following demonstrates only the C++ code involved in manipulating wrapper objects.

Determining a Number Object

CPP code:

#include <string>

static JSVM_Value WrapperObject(JSVM_Env env, JSVM_CallbackInfo info) {
    JSVM_VM vm;
    OH_JSVM_GetVM(env, &vm);

    JSVM_HandleScope handleScope;
    OH_JSVM_OpenHandleScope(env, &handleScope);
    std::string src = R"JS(new Number(42))JS";
    JSVM_Value jsSrc;
    JSVM_Script script;
    JSVM_Value result;

    OH_JSVM_CreateStringUtf8(env, src.c_str(), JSVM_AUTO_LENGTH, &jsSrc);
    OH_JSVM_CompileScript(env, jsSrc, nullptr, 0, true, nullptr, &script);
    OH_JSVM_RunScript(env, script, &result);
    bool isNumberObject = false;
    OH_JSVM_IsNumberObject(env, result, &isNumberObject);
    OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_IsNumberObject: %{public}d\n", isNumberObject);
    OH_JSVM_CloseHandleScope(env, handleScope);

    return nullptr;
}

static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = WrapperObject},
};

static JSVM_CallbackStruct *method = param;

// Alias for the wrapperObject method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"wrapperObject", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(wrapperObject();)JS";

Expected result: