HarmonyOS JavaScript GUI Development Guide

This article provides a comprehensive overview of HarmonyOS, Huawei's distributed operating system that uses JavaScript as its IoT application development language. The author explains what HarmonyOS is, how it differs from Android, and its impact on developers.

HarmonyOS is described as a "future-oriented" distributed operating system designed for all scenarios including mobile office, sports health, social communication, and media entertainment. Unlike traditional single-device systems, HarmonyOS introduces a distributed concept that supports multiple terminal forms including phones, tablets, wearables, smart screens, vehicle systems, PCs, smart speakers, headphones, and AR/VR glasses.

The article compares HarmonyOS with Android across several dimensions:

Usage Scenarios: HarmonyOS is a full-scenario distributed OS while Android primarily targets phones. HarmonyOS uses distributed soft bus technology enabling devices to communicate, exchange data, and call remote services within a local network.

Technical Architecture: While both systems have similar overall architectures, HarmonyOS uses the Ark compiler to compile high-level languages directly to machine code, bypassing the virtual machine. This compilation happens during development rather than on the user's device.

Compilation Method: Android uses a combination of interpretation, JIT, and AOT compilation, while HarmonyOS uses the Ark compiler for cross-platform compilation.

App Development: HarmonyOS supports multiple development languages including Java, XML, C/C++, JavaScript, CSS, and HML (HarmonyOS Markup Language), whereas Android primarily uses Java. HarmonyOS also provides a multi-terminal development IDE for cross-platform development.

The article details the JavaScript UI architecture of HarmonyOS, which consists of three main components: JS Data Binding Framework, JS Runtime, and JS Framework. The JS UI architecture includes Application, Framework, Engine, and Porting Layer components.

For developers, the article explains that HarmonyOS is very friendly to front-end developers, allowing them to use HML+CSS+JavaScript to quickly develop native HarmonyOS apps. The syntax is similar to web development, with HML supporting data binding, event binding, list rendering, conditional rendering, and template references.

The article concludes with practical insights about HarmonyOS development, noting that while it offers excellent cross-platform experience, the mobile OS is still based on AOSP. It recommends using DevEco Studio for development and mentions that the system doesn't support TypeScript yet.

Overall, the article serves as a comprehensive guide for developers interested in understanding and developing for HarmonyOS, particularly those with JavaScript and front-end development backgrounds.