GraphModel.js

export class GraphModel {
  /**
   * @param {Object} attrs Attributes on the GraphModel.
   */
  constructor(attrs) {
    Object.defineProperty(this, 'attrs', { value: attrs, enumerable: false });
    Object.keys(this.attrs).filter(key => !(key in this)).forEach(key => {
      let descriptor;
      if (attrs[key] === null) {
        descriptor = {
          enumerable: true,
          get() {
            return null;
          },
        };
      } else {
        descriptor = {
          enumerable: true,
          get() {
            return this.attrs[key].valueOf();
          },
        };
      }
      Object.defineProperty(this, key, descriptor);
    });
  }
}