Help with Custom State Card

Been studying a lot of custom state card examples, and I get (I think) most of it enough to modify/cobble together the html/javascript to do what I want to do.

However, I don’t really understand the Polymer section, and how to pass entities in. For instance, these two state cards are doing seemingly different things in this section.

Polymer({
    is: 'custom-weather-card',

    properties: {
      hass: {
        type: Object,
      },
      stateObj: {
        type: Object,
      },
      weatherObj: {
        type: Object,
        observer: 'checkRequirements',
        computed: 'comptuteWeatherObj(hass, stateObj)',
      },
    },

    comptuteWeatherObj: function (hass, stateObj) {
      return stateObj && stateObj.attributes && stateObj.attributes.config && stateObj.attributes.config.weather ? hass.states[stateObj.attributes.config.weather] : null;
    },
class StateCardHTML extends window.hassMixins.EventsMixin(Polymer.Element) {
  static get is() { return 'state-card-html'; }
  static get properties() {
    return {
      hass: Object,
      stateObj: Object,
      config: {
        type: Object,
        computed: 'computeConfig(stateObj)',
      },
    };
  }
  static get observers() {
    return [
      'contentChanged(hass.states.*, config)'
    ]
  }
  computeConfig(stateObj) {
    return stateObj && stateObj.attributes && stateObj.attributes.config;
  }

These polymer functions are declared quite differently. And the “computerConfig” or “computeWeatherObj” part I don’t quite understand, I know its passing the entity from hass into polymer, but I don’t understand the syntax.

I guess my question is mainly, if I want to pass in a few entities, or even an array of entities (the second code block is sorta doing that), how do I go about structuring the polymer function?

Polymer docs are your friend
https://meowni.ca/posts/polymer-2-cheatsheet/

https://www.polymer-project.org/2.0/docs/upgrade

Thanks, I went looking for those, but well, you can guess the rest.
I’ll have a look, and see if I have any followup questions.