fetch_attribute.js

import {
    defineWidget,
    log,
    runCallback,
    fetchAttr
} from 'widget-base-helpers';

export default defineWidget('Widget', false, {

    attribute: '', // this key is set in your widget XML
  
    _obj: null,

    constructor() {
        this.log = log.bind(this);
        this.runCallback = runCallback.bind(this);
        this.fetch = fetchAttr.bind(this);
    },

    postCreate() {
        this.log('postCreate', this._WIDGET_VERSION);
    },
  
    update(obj, callback) {
        this._obj = obj;
        this._updateRendering(callback);
    },
  
    async _updateRendering(callback) {
      // A bit more complicated example, where you fetch an attribute (over reference for example).
  
      try {
        // Using async/await is a safe way where you can wait for the fetch.
        const data = await this.fetch(this._obj, this.attribute);
      } catch (e) {
        // Do something with the error;
      }
  
      this.runCallback(callback);
    }
  
  
});

get_attribute.js

import {
    defineWidget,
    log,
    runCallback,
} from 'widget-base-helpers';

export default defineWidget('Widget', false, {

    attribute: '', // this key is set in your widget XML
  
    _obj: null,

    constructor() {
        this.log = log.bind(this);
        this.runCallback = runCallback.bind(this);
    },

    postCreate() {
        this.log('postCreate', this._WIDGET_VERSION);
    },
  
    update(obj, callback) {
      this._obj = obj;
      
      if (this._obj) {
        const value = this._obj.get(this.attribute); // Now you get the value from attribute of the context object;
      }
      
      this.runCallback(callback);
    }
  
  
});