harmony 鸿蒙Working with Primitives Using JSVM-API

  • 2025-06-12
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Working with Primitives Using JSVM-API

Introduction

JSVM-API provides APIs for converting data between C/C++ and JavaScript (JS) data types and obtaining the JS object of the specified type.

Basic Concepts

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

  • Conversion between JS and C/C primitives: You can use JSVM-API to convert JS values to C/C++ data types, for example, convert a JS value into a C/C++ integer and convert a JS string into a C/C++ string array. You can also convert C/C++ data into a JS value and return the JS value to JS.

Available APIs

API Description
OH_JSVM_CoerceToBool Converts a JS value to an object of the Boolean type.
OH_JSVM_CoerceToNumber Converts a JS value to an object of the number type.
OH_JSVM_CoerceToObject Converts a JS value to an object of the object type.
OH_JSVM_CoerceToString Converts a JS value to an object of the string type.
OH_JSVM_GetBoolean Obtains a JS singleton object that is used to represent the given Boolean value.
OH_JSVM_GetValueBool Obtains the C Boolean primitive equivalent of the given JS Boolean.
OH_JSVM_GetGlobal Obtains the global object of the current environment.
OH_JSVM_GetNull Obtains the JS null object.
OH_JSVM_GetUndefined Obtains the JS undefined 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 primitive development.

OH_JSVM_CoerceToBool

Call OH_JSVM_CoerceToBool to forcibly convert a JS value to a JS Boolean value.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_CoerceToBool.
static JSVM_Value CoerceToBool(JSVM_Env env, JSVM_CallbackInfo info)
{
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    JSVM_Value boolean = nullptr;
    JSVM_Status status = OH_JSVM_CoerceToBool(env, args[0], &boolean);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_CoerceToBool failed");
    } else {
        bool result = false;
        OH_JSVM_GetValueBool(env, boolean, &result);
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_CoerceToBool success:%{public}d", result);
    }
    return boolean;
}
// Register the CoerceToBool callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = CoerceToBool},
};
static JSVM_CallbackStruct *method = param;
// Alias for the CoerceToBool method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"coerceToBool", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(coerceToBool("123"))JS";

Expected result:

SVM OH_JSVM_CoerceToBool success:1

OH_JSVM_CoerceToNumber

Call OH_JSVM_CoerceToNumber to forcibly convert a JS value to a JS number.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_CoerceToNumber.
static JSVM_Value CoerceToNumber(JSVM_Env env, JSVM_CallbackInfo info)
{
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    JSVM_Value number = nullptr;
    JSVM_Status status = OH_JSVM_CoerceToNumber(env, args[0], &number);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_CoerceToNumber failed");
    } else {
        int32_t result = 0;
        OH_JSVM_GetValueInt32(env, number, &result);
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_CoerceToNumber success:%{public}d", result);
    }
    return number;
}
// Register the CoerceToNumber callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = CoerceToNumber},
};
static JSVM_CallbackStruct *method = param;
// Alias for the CoerceToNumber method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"coerceToNumber", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(coerceToNumber(true))JS";

Expected result:

JSVM OH_JSVM_CoerceToNumber success:1

OH_JSVM_CoerceToObject

Call OH_JSVM_CoerceToObject to forcibly convert a JS value to a JS object.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_CoerceToObject.
static JSVM_Value CoerceToObject(JSVM_Env env, JSVM_CallbackInfo info)
{
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    JSVM_Value obj = nullptr;
    JSVM_Status status = OH_JSVM_CoerceToObject(env, args[0], &obj);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_CoerceToObject failed");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_CoerceToObject success");
    }
    return obj;
}
// Register the CoerceToObject callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = CoerceToObject},
};
static JSVM_CallbackStruct *method = param;
// Alias for the CoerceToObject method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"coerceToObject", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(coerceToObject(123))JS";

Expected result:

JSVM OH_JSVM_CoerceToObject success

OH_JSVM_CoerceToString

Call OH_JSVM_CoerceToString to forcibly convert a JS value to a JS string.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_CoerceToString.
static JSVM_Value CoerceToString(JSVM_Env env, JSVM_CallbackInfo info)
{
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    JSVM_Value str = nullptr;
    JSVM_Status status = OH_JSVM_CoerceToString(env, args[0], &str);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_CoerceToString fail");
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_CoerceToString success");
    }
    return str;
}
// Register the CoerceToString callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = CoerceToString},
};
static JSVM_CallbackStruct *method = param;
// Alias for the CoerceToString method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"coerceToString", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(coerceToString(22222))JS";

Expected result:

JSVM OH_JSVM_CoerceToString success

OH_JSVM_GetBoolean

Call OH_JSVM_GetBoolean to obtain a JS singleton object that is used to represent the given Boolean value.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_GetBoolean.
static JSVM_Value GetBoolean(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Pass in two parameters and parse them.
    size_t argc = 2;
    JSVM_Value argv[2] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, argv, nullptr, nullptr);
    int32_t paramData = 0;
    OH_JSVM_GetValueInt32(env, argv[0], &paramData);
    int32_t paramValue = 0;
    OH_JSVM_GetValueInt32(env, argv[1], &paramValue);
    JSVM_Value returnValue = nullptr;
    bool type = false;
    if (paramData == paramValue) {
        OH_LOG_INFO(LOG_APP, "JSVM resultType equal");
        type = true;
    }
    JSVM_Status status = OH_JSVM_GetBoolean(env, type, &returnValue);
    if (status != JSVM_OK) {
        OH_JSVM_ThrowError(env, nullptr, "JSVM OH_JSVM_CoerceToNumber fail");
    } else {
        bool result = false;
        OH_JSVM_GetValueBool(env, returnValue, &result);
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_CoerceToNumber success:%{public}d", result);
    }
    // Return the result.
    return returnValue;
}
// Register the GetBoolean callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetBoolean},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetBoolean method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getBoolean", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(getBoolean(1, 2);
                                 getBoolean(1, 1))JS";

Expected result:

JSVM OH_JSVM_CoerceToNumber success:0
JSVM resultType equal
JSVM OH_JSVM_CoerceToNumber success:1

OH_JSVM_GetValueBool

Call OH_JSVM_GetValueBool to obtain the C Boolean primitive equivalent of the given JS Boolean.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_GetValueBool.
static JSVM_Value GetValueBool(JSVM_Env env, JSVM_CallbackInfo info)
{
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    bool result = false;
    JSVM_Status status = OH_JSVM_GetValueBool(env, args[0], &result);
    if (status == JSVM_BOOLEAN_EXPECTED||status != JSVM_OK) {
        // If OH_JSVM_GetValueBool is successful, JSVM_OK is returned. If a non-Boolean value is passed in, JSVM_BOOLEAN_EXPECTED is returned.
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_GetValueBool fail:%{public}d", status);
        return nullptr;
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_GetValueBool success:%{public}d", result);
    }
    JSVM_Value boolJv = nullptr;
    OH_JSVM_GetBoolean(env, result, &boolJv);
    return boolJv;
}
// Register the GetValueBool callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetValueBool},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetValueBool method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getValueBool", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(getValueBool("abc");
                                getValueBool(true);
                                getValueBool(false);)JS";

Expected result:

JSVM OH_JSVM_GetValueBool fail:7
JSVM OH_JSVM_GetValueBool success:1
JSVM OH_JSVM_GetValueBool success:0

OH_JSVM_GetGlobal

Call OH_JSVM_GetGlobal to obtain a JS global object. You can use this API to obtain the JSVM_Value that represents a JS global object, so that the JSVM module can interact with the global variables and functions defined in the JS context.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_GetGlobal.
static JSVM_Value GetGlobal(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the global object.
    JSVM_Value value = nullptr;
    JSVM_Value global = nullptr;
    OH_JSVM_CreateInt32(env, 1, &value);
    JSVM_Status status = OH_JSVM_GetGlobal(env, &global);
    OH_JSVM_SetNamedProperty(env, global, "Row", value);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_GetGlobal fail");
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_GetGlobal success");
    }
    return global;
}
// Register the GetGlobal callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetGlobal},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetGlobal method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getGlobal", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(getGlobal())JS";

Expected result:

JSVM OH_JSVM_GetGlobal success

OH_JSVM_GetNull

Call OH_JSVM_GetNull to obtain a JS null object.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_GetNull.
static JSVM_Value GetNull(JSVM_Env env, JSVM_CallbackInfo info) {
    JSVM_Value nullValue = nullptr;
    JSVM_Status status = OH_JSVM_GetNull(env, &nullValue);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_GetNull fail");
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_GetNull success");
    }
    return nullValue;
}
// Register the GetNull callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetNull},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetNull method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getNull", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(getNull())JS";

Expected result:

JSVM OH_JSVM_GetNull success

OH_JSVM_GetUndefined

Call OH_JSVM_GetUndefined to obtain a JS undefined object.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_GetUndefined.
static JSVM_Value GetUndefined(JSVM_Env env, JSVM_CallbackInfo info)
{
    //Obtain and parse the input parameters.
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // Create the value 'undefined'.
    JSVM_Value value = nullptr;
    JSVM_Status status = OH_JSVM_GetUndefined(env, &value);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_GetUndefined failed");
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_GetUndefined success");
    }
    return value;
}
// Register the GetUndefined callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = GetUndefined},
};
static JSVM_CallbackStruct *method = param;
// Alias for the GetUndefined method to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"getUndefined", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call C++ code from JS.
const char *srcCallNative = R"JS(getUndefined())JS";

Expected result:

JSVM OH_JSVM_GetUndefined success

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