Why does uniapp run slowly?

With the continuous growth of mobile Internet users, the mobile application market has shown explosive growth. In order to cater to this trend, many developers have chosen cross-platform development technology and published applications on multiple platforms in order to promote their applications to a wider audience. UniApp is one of the cross-platform development technologies, which can run on both iOS and Android platforms.

However, in the process of developing applications using UniApp, many developers find that the application runs too slowly. This is a very serious problem, because slow speed will not only bring a bad user experience to users, but also affect the market competitiveness of the application. Therefore, how to improve the running speed of UniApp has become a matter of great concern to developers.

First, we need to understand why UniApp is slow. UniApp is developed based on the WeChat applet. When the WeChat applet is running, the rendering of the page and the processing of data are implemented through the JavaScript language. Therefore, UniApp also adopts this operating mechanism. However, due to the special nature of the JavaScript language, its efficiency is relatively low, resulting in the problem that UniApp is relatively slow when running.

During the running of UniApp, performance bottlenecks mainly lie in the following aspects:

1. Memory problem: Since UniApp uses Webview to render the page, Webview is a separate process, so the page The transfer of data between them requires the use of memory, and the slowness of memory will cause the page to run slower.
2. UI rendering problem: Due to the different UI rendering mechanisms of each UniApp platform, performance problems may occur when rendering and updating the page.
3. Operation logic problem: Because the template logic of UniApp is relatively complex and the compiler's operating efficiency is not high, the initial loading time of the page is relatively long.

Below, we list some methods to improve the running speed of UniApp.

1. Reduce repeated rendering

In UniApp, component updates are completed by the virtual DOM. The virtual DOM will be updated multiple times per second, and data will be rendered and compared during the update. If there are repeated rendering operations, performance will be wasted. Therefore, developers can use the "shouldComponentUpdate" function to optimize the component's rendering process and reduce repeated rendering.

2. Avoid using setData

setData is a method used to update page data. It will re-render the updated data to the page every time it is called. However, if there is too much data on the page, using setData will cause performance degradation. Therefore, developers should avoid frequently using setData to update data, try to save data locally, and reduce the number of calls to setData.

3. Use mini program cloud development

Mini program cloud development is an important function of UniApp, which can be used to store data, build servers, etc. Using mini program cloud development can reduce the time consumed by applications when requesting data and accessing external services, and improve the running speed of applications.

4. Reasonable use of cache

The cache in UniApp can effectively avoid repeated requests and loading, thereby improving the operating efficiency of the application. Developers can cache data locally based on business needs and read data directly from the local during the next load to avoid repeated requests and loads.

5. Use canvas instead of DOM operation

DOM operation is one of the very time-consuming operations in UniApp. In some scenarios, using canvas instead of DOM operations can improve page rendering speed. Developers can use canvas to draw static effects on DOM elements that need to be modified frequently, thereby reducing the frequency of DOM operations.

In short, there are indeed some problems with the running speed of UniApp, but this does not mean that developers cannot solve them. Through the above optimization strategies, the running speed of UniApp can be effectively improved, making the application smoother and faster, thus improving the market competitiveness of the application.

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