Pay attention to the following points when developing small programs by yourself:

Js and json are essential files for small programs;

Except app.js, other js files must have Page({}), otherwise an error will be reported;

The server domain name must be https；;

In the past, when the applet created a new project, it chose not to have APPId, so it can call other domain name interfaces in the program. But now, maybe the version has been updated, and I tested it, so I can't call it, and there is a 403 error:

When assigning values to colors in js, you need to use hexadecimal instead of "red" and "white".

"Without AppID", it is impossible to debug the code on the real machine, but it does not affect the development.

Sublime Text software is used for development, and it is better to display it with WeChat developer tools.