discourse/app/assets/javascripts/wizard/components/wizard-field-checkboxes.js

import Component from "@ember/component";
import { set } from "@ember/object";

export default Component.extend({
  init(...args) {
    this._super(...args);
    this.set("field.value", this.field.value || []);

    for (let choice of this.field.choices) {
      if (this.field.value.includes(choice.id)) {
        set(choice, "checked", true);
      }
    }
  },
  actions: {
    changed(checkbox) {
      let newFieldValue = this.field.value;
      const checkboxValue = checkbox.parentElement
        .getAttribute("value")
        .toLowerCase();

      if (checkbox.checked) {
        newFieldValue.push(checkboxValue);
      } else {
        const index = newFieldValue.indexOf(checkboxValue);
        if (index > -1) {
          newFieldValue.splice(index, 1);
        }
      }
      this.set("field.value", newFieldValue);
    }
  }
});