Setting JS Object Properties Using JSVM-API

Introduction

This topic walks you through on how to obtain and set properties of a JavaScript (JS) object using JSVM-API. Properly using these APIs help to implement more complex functionalities and logic.

Basic Concepts

Before working with JS objects using JSVM-API, you need to understand the following concepts:

• Object: a composite data type that allows values of different types in an independent entity in JS. An object is a collection of properties and methods. A property is a value associated with the object, and a method is an operation that the object can perform.
• Property: a feature, in the key-value format, of an object in JS. Each property has a name (key or identifier) and a value. The property value can be of any data type, including the basic type, object, and function.
• Enumerable property: a property in JS with enumerable set to true. An enumerable property can be traversed by for...in.
• Own property: a property defined for an object rather than inherited from the prototype chain.

Available APIs

API	Description
OH_JSVM_GetPropertyNames	Obtains the names of all enumerable properties of a JS object as a JS array.
OH_JSVM_SetProperty	Sets a property for a JS object.
OH_JSVM_GetProperty	Obtains a property from a JS object.
OH_JSVM_HasProperty	Checks whether a JS object has the specified property.
OH_JSVM_DeleteProperty	Deletes a property from a JS object.
OH_JSVM_HasOwnProperty	Checks whether an object has the own property with the specified name.
OH_JSVM_SetNamedProperty	Sets a property with the given property name for a JS object. This API is equivalent to calling OH_JSVM_SetProperty with a JSVM_Value created from the string passed in as utf8Name.
OH_JSVM_GetNamedProperty	Obtains a property from a JS object. This API is equivalent to calling OH_JSVM_GetProperty with a JSVM_Value created from the string passed in as utf8Name.
OH_JSVM_HasNamedProperty	Checks whether a JS object has the specified property. This API is equivalent to calling OH_JSVM_HasProperty with a JSVM_Value created from the string passed in as utf8Name.
OH_JSVM_DefineProperties	Defines multiple properties for a JS object.
OH_JSVM_GetAllPropertyNames	Obtains the names of all available properties of a JS object as a JS array.

Example

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

OH_JSVM_GetPropertyNames

Call OH_JSVM_GetPropertyNames to obtain names of all enumerable properties of a JS object in the form of a string array. If the operation is successful, JSVM_OK is returned.

CPP code:

// Define OH_JSVM_GetPropertyNames.
static JSVM_Value GetPropertyNames(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Pass in obj as a parameter.
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // Obtain the names of all the enumerable properties of the object in the form of a string array and output the string array in result.
    JSVM_Value result = nullptr;
    JSVM_Status status = OH_JSVM_GetPropertyNames(env, args[0], &result);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "Failed to get propertynames");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_GetPropertyNames success");
    }
    return result;
}
// Register the GetPropertyNames callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetPropertyNames},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetPropertyNames method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getPropertyNames", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = '{ data: 0, message: "hello world"}';
    let script = getPropertyNames(obj);
)JS";

Expected result:

JSVM OH_JSVM_GetPropertyNames success

OH_JSVM_SetProperty

Call OH_JSVM_SetProperty to set a property for an object.

CPP code:

// Define OH_JSVM_SetProperty.
static JSVM_Value SetProperty(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the parameters passed from JS. The first parameter specifies the object, the second parameter specifies the property name, and the third parameter specifies the property value to set.
    size_t argc = 3;
    JSVM_Value args[3] = {nullptr};
    JSVM_Status status = OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_GetCbInfo fail");
        return nullptr;
    }
    // Call OH_JSVM_SetProperty to set the property name and value to the object. If the operation fails, an error is thrown.
    status = OH_JSVM_SetProperty(env, args[0], args[1], args[2]);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_SetProperty fail");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_SetProperty success");
    }
    // Return the object that is successfully set.
    return args[0];
}
// Register the SetProperty callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = SetProperty},
};
static JSVM_CallbackStruct *method = param;
// Alias for the SetProperty method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"setProperty", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = { data: 0, message: "hello world", 50: 1};
    setProperty(obj, "code", "hi")
)JS";

Expected result:

JSVM OH_JSVM_SetProperty success

OH_JSVM_GetProperty

Call OH_JSVM_GetProperty to obtain a property value of a JS object based on the property name.

CPP code:

// Define OH_JSVM_GetProperty.
static JSVM_Value GetProperty(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the two parameters passed from JS.
    size_t argc = 2;
    JSVM_Value args[2] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // The first parameter specifies the target object, and the second specifies the property name. Call OH_JSVM_GetProperty to obtain the value of the property.
    JSVM_Value result = nullptr;
    JSVM_Status status = OH_JSVM_GetProperty(env, args[0], args[1], &result);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_GetProperty fail");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_GetProperty success");
    }
    return result;
}
// Register the GetProperty callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetProperty},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetProperty method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getProperty", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = { data: 0, message: "hello world", 50: 1};
    getProperty(obj, "message")
)JS";

Expected result:

JSVM OH_JSVM_GetProperty success

OH_JSVM_HasProperty

Call OH_JSVM_HasProperty to check whether an object has the specified property. This can prevent the exception or error caused by access to a property that does not exist.

CPP code:

// Define OH_JSVM_HasProperty.
static JSVM_Value HasProperty(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Pass in two parameters from JS. The first parameter specifies the target object, and the second parameter specifies the property to check.
    size_t argc = 2;
    JSVM_Value args[2] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // Pass the parameters to OH_JSVM_HasProperty. If the API is successfully called, convert the result to JSVM_Value and return JSVM_Value. Otherwise, throw an error.
    bool result = false;
    JSVM_Status status = OH_JSVM_HasProperty(env, args[0], args[1], &result);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_HasProperty fail");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_HasProperty success:%{public}d", result);
    }
    // If the property exists in the object, output true, convert the result to JSVM_Value, and return JSVM_Value.
    JSVM_Value returnResult = nullptr;
    OH_JSVM_GetBoolean(env, result, &returnResult);
    return returnResult;
}
// Register the HasProperty callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = HasProperty},
};
static JSVM_CallbackStruct *method = param;
// Alias for the HasProperty method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"hasProperty", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = { data: 0, message: "hello world", 50: 1};
    hasProperty(obj, "data")
    hasProperty(obj, 0)
)JS";

Expected result:

// hasProperty (obj, "data") output
JSVM OH_JSVM_HasProperty success:1
// Output of hasProperty (obj, 0).
JSVM OH_JSVM_HasProperty success:0

OH_JSVM_DeleteProperty

Call OH_JSVM_DeleteProperty to delete the property specified by key from an object.

If the object is a non-extensible object or the property is not configurable, the property cannot be deleted.

CPP code:

// Define OH_JSVM_DeleteProperty.
static JSVM_Value DeleteProperty(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the two parameters passed from JS.
    size_t argc = 2;
    JSVM_Value args[2] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    JSVM_ValueType valueType;
    OH_JSVM_Typeof(env, args[0], &valueType);
    if (valueType != JSVM_OBJECT) {
        OH_JSVM_ThrowError(env, nullptr, "Expects an object as argument.");
        return nullptr;
    }
    // Delete the specified property from the object and return a bool value indicating whether the deletion is successful.
    bool result = false;
    JSVM_Status status = OH_JSVM_DeleteProperty(env, args[0], args[1], &result);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_DeleteProperty failed");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_DeleteProperty success:%{public}d", result);
    }
    // Convert the bool value to JSVM_value and return JSVM_value.
    JSVM_Value ret;
    OH_JSVM_GetBoolean(env, result, &ret);
    return ret;
}
// Register the DeleteProperty callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = DeleteProperty},
};
static JSVM_CallbackStruct *method = param;
// Alias for the DeleteProperty method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"deleteProperty", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = { data: 0, message: "hello world", 50: 1};
    deleteProperty(obj, "message")
)JS";

Expected result:

JSVM OH_JSVM_DeleteProperty success:1

OH_JSVM_HasOwnProperty

Call OH_JSVM_HasOwnProperty to check whether a JS object has its own property.

CPP code:

// Define OH_JSVM_HasOwnProperty.
static JSVM_Value HasOwnProperty(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the two parameters passed from JS.
    size_t argc = 2;
    JSVM_Value args[2] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // Check whether the first parameter is an object.
    JSVM_ValueType valueType1;
    OH_JSVM_Typeof(env, args[0], &valueType1);
    if (valueType1 != JSVM_OBJECT) {
        OH_JSVM_ThrowError(env, nullptr, "First argument must be an object.");
        return nullptr;
    }
    // Check whether the second parameter is a string.
    JSVM_ValueType valuetype2;
    OH_JSVM_Typeof(env, args[1], &valuetype2);
    if (valuetype2 != JSVM_STRING ) {
        OH_JSVM_ThrowError(env, nullptr, "Second argument must be a string.");
        return nullptr;
    }
    // Check whether the object has the specified property. The result is in hasProperty.
    bool hasProperty = false;
    JSVM_Status status = OH_JSVM_HasOwnProperty(env, args[0], args[1], &hasProperty);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_HasOwnProperty failed");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_HasOwnProperty success:%{public}d", hasProperty);
    }
    // Convert the bool value to JSVM_Value and return JSVM_value.
    JSVM_Value result;
    OH_JSVM_GetBoolean(env, hasProperty, &result);
    return result;
}
// Register the HasOwnProperty callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = HasOwnProperty},
};
static JSVM_CallbackStruct *method = param;
// Alias for the HasOwnProperty method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"hasOwnProperty", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = { data: 0, message: "hello world", 50: 1};
    hasOwnProperty(obj, "message")
    hasOwnProperty(obj, "__defineGetter__")
)JS";

Expected result:

// hasOwnProperty (obj, "message") output
JSVM OH_JSVM_HasOwnProperty success:1
// hasOwnProperty(obj, "__defineGetter__") output
// `__defineGetter__` is the prototype method of the object, not OwnProperty. The expected return value is 0.
JSVM OH_JSVM_HasOwnProperty success:0

OH_JSVM_SetNamedProperty

Call OH_JSVM_SetNamedProperty to set a property for a JS object.

CPP code:

// Define OH_JSVM_SetNamedProperty.
static JSVM_Value SetNamedProperty(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the parameter passed from JS.
    size_t argc = 1;
    JSVM_Value str;
    char strKey[32] = "";
    OH_JSVM_GetCbInfo(env, info, &argc, &str, nullptr, nullptr);
    // Obtain the string passed in and store it in strKey.
    size_t keyLength = 0;
    OH_JSVM_GetValueStringUtf8(env, str, strKey, 32, &keyLength);
    // Create an object.
    JSVM_Value newObj;
    OH_JSVM_CreateObject(env, &newObj);
    // Set the property value to 1234.
    int32_t value = 1234;
    JSVM_Value numValue;
    OH_JSVM_CreateInt32(env, value, &numValue);
    // Associate the integer value with the property name.
    JSVM_Status status = OH_JSVM_SetNamedProperty(env, newObj, strKey, numValue);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_SetNamedProperty failed");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_SetNamedProperty success");
    }
    // Return the newly created object with the property set.
    return newObj;
}
// Register the SetNamedProperty callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = SetNamedProperty},
};
static JSVM_CallbackStruct *method = param;
// Alias for the SetNamedProperty method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"setNamedProperty", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

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

Expected result:

JSVM OH_JSVM_SetNamedProperty success

OH_JSVM_GetNamedProperty

Call OH_JSVM_GetNamedProperty to obtain the value of the specified property from a JS object.

CPP code:

// Define OH_JSVM_GetNamedProperty.
static JSVM_Value GetNamedProperty(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the two parameters passed from JS.
    size_t argc = 2;
    JSVM_Value args[2] = {nullptr};
    char strKey[32] = "";
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // Obtain the name of the property to obtain.
    size_t keyLength = 0;
    OH_JSVM_GetValueStringUtf8(env, args[1], strKey, 32, &keyLength);
    // Obtain the value of the property and store it in result.
    JSVM_Value result;
    JSVM_Status status = OH_JSVM_GetNamedProperty(env, args[0], strKey, &result);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_GetNamedProperty failed");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_GetNamedProperty success");
    }
    return result;
}
// Register the GetNamedProperty callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetNamedProperty},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetNamedProperty method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getNamedProperty", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = { data: 0, message: "hello world", 50: 1};
    getNamedProperty(obj, "message")
)JS";

Expected result:

JSVM OH_JSVM_GetNamedProperty success

OH_JSVM_HasNamedProperty

Call OH_JSVM_HasNamedProperty to check whether a JS object contains the specified property.

CPP code:

// Define OH_JSVM_HasNamedProperty.
static JSVM_Value HasNamedProperty(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the two parameters passed from JS.
    size_t argc = 2;
    JSVM_Value args[2] = {nullptr};
    char strKey[32] = "";
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // Obtain the property name.
    size_t keyLength = 0;
    OH_JSVM_GetValueStringUtf8(env, args[1], strKey, 32, &keyLength);
    // Check whether the object has the specified property. The result is in hasProperty.
    bool hasProperty = false;
    JSVM_Status status = OH_JSVM_HasNamedProperty(env, args[0], strKey, &hasProperty);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_HasNamedProperty failed");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_HasNamedProperty success:%{public}d", hasProperty);
    }
    // Convert the bool value to JSVM_Value and return JSVM_value.
    JSVM_Value result;
    OH_JSVM_GetBoolean(env, hasProperty, &result);
    return result;
}
// Register the HasNamedProperty callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = HasNamedProperty},
};
static JSVM_CallbackStruct *method = param;
// Alias for the HasNamedProperty method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"hasNamedProperty", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = { data: 0, message: "hello world", 50: 1};
    hasNamedProperty(obj, "message")
)JS";

Expected result:

JSVM OH_JSVM_HasNamedProperty success:1

OH_JSVM_DefineProperties

Call OH_JSVM_DefineProperties to customize one or more properties for an object.

CPP code:

#include <fstream>
#include <string>
// Callback for defineMethodPropertiesExample in the property descriptor list.
static JSVM_Value DefineMethodPropertiesExample(JSVM_Env env, JSVM_CallbackInfo info)
{
    int32_t propValue = 26;
    JSVM_Value returnValue;
    OH_JSVM_CreateInt32(env, propValue, &returnValue);
    return returnValue;
}
// Callback for getterCallback in the property descriptor list.
static JSVM_Value GetterCallback(JSVM_Env env, JSVM_CallbackInfo info)
{
    JSVM_Value result;
    const char *str = "Hello world!";
    size_t length = strlen(str);
    // Create property values.
    OH_JSVM_CreateStringUtf8(env, str, length, &result);
    return result;
}

// Function to execute a JS string.
static JSVM_Value RunScriptAndLogResult(JSVM_Env env, const std::string &srcCode) {
    JSVM_Value sourceCodeValue;
    OH_JSVM_CreateStringUtf8(env, srcCode.c_str(), srcCode.size(), &sourceCodeValue);
    JSVM_Script script;
    // Compile the JS code string and return the compiled script.
    OH_JSVM_CompileScript(env, sourceCodeValue, nullptr, 0, true, nullptr, &script);
    JSVM_Value jsVmResult;
    // Execute the JS script.
    OH_JSVM_RunScript(env, script, &jsVmResult);
    return jsVmResult;
}

// Define OH_JSVM_DefineProperties.
static JSVM_Value DefineProperties(JSVM_Env env, JSVM_CallbackInfo info) {
    // Obtain an empty object passed from JS.
    size_t argc = 1;
    JSVM_Value argv[1] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, argv, nullptr, nullptr);
    // Create a property value of the string type.
    JSVM_Value stringValue;
    OH_JSVM_CreateStringUtf8(env, "Hello!", JSVM_AUTO_LENGTH, &stringValue);
    // Create the callback lists corresponding to the property descriptors.
    JSVM_CallbackStruct param[] = {
        {.data = nullptr, .callback = DefineMethodPropertiesExample},
        {.data = nullptr, .callback = GetterCallback},

    };
    // Create a property descriptor list. For details, see the definition of JSVM_PropertyDescriptor.
    JSVM_PropertyDescriptor descriptor[] = {
        // Define a property value of the method type.
        {"defineMethodPropertiesExample", nullptr, &param[0], nullptr, nullptr, nullptr, JSVM_DEFAULT},
        // Define the property value of the string type.
        {"defineStringPropertiesExample", nullptr, nullptr, nullptr, nullptr, stringValue, JSVM_DEFAULT},
        // Define the property value of the getter type.
        {"getterCallback", nullptr, nullptr, &param[1], nullptr, nullptr,JSVM_DEFAULT}};
    // Create properties for the obj object based on the property descriptor list.
    JSVM_Status statusProperty;
    statusProperty = OH_JSVM_DefineProperties(env, *argv, sizeof(descriptor) / sizeof(descriptor[0]), descriptor);
    if (statusProperty != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM DefineProperties fail");
        return nullptr;
    }
    // Call the properties added to the obj object.
    // Run obj.defineMethodPropertiesExample() and return the result to JS.
    static std::string srcMethod;
    srcMethod = R"JS(obj.defineMethodPropertiesExample();)JS";
    JSVM_Value jsVmResult = RunScriptAndLogResult(env, srcMethod);
    if (jsVmResult != nullptr) {
        int32_t number;
        OH_JSVM_GetValueInt32(env, jsVmResult, &number);
        OH_LOG_INFO(LOG_APP, "JSVM DefineMethodPropertiesExample success:%{public}d", number);
    }
    // Run obj.defineStringPropertiesExample() and return the result to JS.
    static std::string srcString;
    srcString = R"JS(obj.defineStringPropertiesExample;)JS";
    JSVM_Value jsVmResult1 = RunScriptAndLogResult(env, srcString);
    if (jsVmResult1 != nullptr) {
        size_t length = 0;
        OH_JSVM_GetValueStringUtf8(env, jsVmResult1, nullptr, 0, &length);
        char *buf = (char *)malloc(length + 1);
        if (buf == nullptr) {
            OH_LOG_ERROR(LOG_APP, "malloc failed");
            return nullptr;
        }
        memset(buf, 0, length + 1);
        OH_JSVM_GetValueStringUtf8(env, jsVmResult1, buf, length + 1, &length);
        OH_LOG_INFO(LOG_APP, "JSVM defineStringPropertiesExample success:%{public}s", buf);
        free(buf);
    }
    // Call getterCallback() of obj and return the result string to JS.
    static std::string srcGetter;
    srcGetter = R"JS(obj.getterCallback;)JS";
    JSVM_Value jsVmResult2 = RunScriptAndLogResult(env, srcGetter);
    if (jsVmResult2 != nullptr) {
        size_t length = 0;
        OH_JSVM_GetValueStringUtf8(env, jsVmResult2, nullptr, 0, &length);
        char *buf = (char *)malloc(length + 1);
        if (buf == nullptr) {
            OH_LOG_ERROR(LOG_APP, "malloc failed");
            return nullptr;
        }
        memset(buf, 0, length + 1);
        OH_JSVM_GetValueStringUtf8(env, jsVmResult2, buf, length + 1, &length);
        OH_LOG_INFO(LOG_APP, "JSVM getterCallback success:%{public}s", buf);
        free(buf);
    }
    return jsVmResult;
}

// Register the DefineProperties callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = DefineProperties},
};
static JSVM_CallbackStruct *method = param;
// Alias for the DefineProperties method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"defineProperties", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = {};
    defineProperties(obj)
)JS";

Expected result:

JSVM DefineMethodPropertiesExample success:26
JSVM defineStringPropertiesExample success:Hello!
JSVM getterCallback success:Hello world!

OH_JSVM_GetAllPropertyNames

Call OH_JSVM_GetAllPropertyNames to obtain the names of all enumerable properties of a JS object as a JS array.

CPP code:

// Define OH_JSVM_GetAllPropertyNames.
static JSVM_Value GetAllPropertyNames(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the parameter passed from JS.
    size_t argc = 1;
    JSVM_Value args[1];
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // Obtain names of all properties (own properties) of the specified object.
    JSVM_Value result;
    JSVM_Status status = OH_JSVM_GetAllPropertyNames(env, args[0],
                                         JSVM_KeyCollectionMode::JSVM_KEY_OWN_ONLY,
                                         JSVM_KeyFilter::JSVM_KEY_WRITABLE,
                                         JSVM_KeyConversion::JSVM_KEY_NUMBERS_TO_STRINGS, &result);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "Failed to get allpropertynames");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_GetAllPropertyNames success");
    }
    return result;
}
// Register the GetAllPropertyNames callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetAllPropertyNames},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetAllPropertyNames method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getAllPropertyNames", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};

// Call the C++ code from JS.
const char *srcCallNative = R"JS(
    let obj = '{ data: 0, message: "hello world", 50: 1}';
    let script = getAllPropertyNames(obj);
)JS";

Expected result:

JSVM OH_JSVM_GetAllPropertyNames success