litemall/litemall-wx/lib/vant-weapp/mixins/observer/index.js

import { behavior } from './behavior';
export function observe(vantOptions, options) {
    const { watch } = vantOptions;
    options.behaviors.push(behavior);
    if (watch) {
        const props = options.properties || {};
        Object.keys(watch).forEach(key => {
            if (key in props) {
                let prop = props[key];
                if (prop === null || !('type' in prop)) {
                    prop = { type: prop };
                }
                prop.observer = watch[key];
                props[key] = prop;
            }
        });
        options.properties = props;
    }
}