Comparing JS Values Using JSVM-API

Introduction

This topic walks you through on how to use JSVM-API to check whether two JavaScript (JS) values are strictly equal (equal in both value and type). The API provided is equivalent to the JS strict equality operator (===). This API avoids type conversion and loose equality comparison, ensuring equal values and types.

Basic Concepts

Strictly equal: If two values are strictly equal, they are equal in both value and type. When type conversion is considered, if the values being compared are of different types, false will be returned even if the values are the same.

Available APIs

API	Description
OH_JSVM_StrictEquals	Checks whether two JSVM_Value objects are strictly equal.

Example

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

OH_JSVM_StrictEquals

Use OH_JSVM_StrictEquals to check whether two JS values are strictly equal.

CPP code:

// hello.cpp
#include "napi/native_api.h"
#include "ark_runtime/jsvm.h"
#include <hilog/log.h>
// Define OH_JSVM_StrictEquals.
static JSVM_Value IsStrictEquals(JSVM_Env env, JSVM_CallbackInfo info)
{
    // Obtain the input parameters.
    size_t argc = 2;
    JSVM_Value args[2] = {nullptr};
    OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr);
    // Call OH_JSVM_StrictEquals to check whether two given JS values are strictly equal.
    bool result = false;
    JSVM_Status status = OH_JSVM_StrictEquals(env, args[0], args[1], &result);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_StrictEquals: failed");
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_StrictEquals: success: %{public}d", result);
    }
    JSVM_Value isStrictEqual = nullptr;
    OH_JSVM_GetBoolean(env, result, &isStrictEqual);
    return isStrictEqual;
}
// Register the IsStrictEquals callback.
static JSVM_CallbackStruct param[] = {
    {.data = nullptr, .callback = IsStrictEquals},
};
static JSVM_CallbackStruct *method = param;
// Set a property descriptor named isStrictEquals and associate it with a callback. This allows the isStrictEquals callback to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"isStrictEquals", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
};
// Call the C++ code from JS.
const char* srcCallNative = R"JS(data = '123';value = '123';isStrictEquals(data,value);)JS";

Expected result:

JSVM OH_JSVM_StrictEquals: success: 1