frontend/js/common/entity/compute_state_display.js

import computeStateDomain from './compute_state_domain.js';
import formatDateTime from '../datetime/format_date_time.js';
import formatDate from '../datetime/format_date.js';
import formatTime from '../datetime/format_time.js';

export default function computeStateDisplay(localize, stateObj, language) {
  if (!stateObj._stateDisplay) {
    const domain = computeStateDomain(stateObj);
    if (domain === 'binary_sensor') {
      // Try device class translation, then default binary sensor translation
      if (stateObj.attributes.device_class) {
        stateObj._stateDisplay =
          localize(`state.${domain}.${stateObj.attributes.device_class}.${stateObj.state}`);
      }
      if (!stateObj._stateDisplay) {
        stateObj._stateDisplay = localize(`state.${domain}.default.${stateObj.state}`);
      }
    } else if (stateObj.attributes.unit_of_measurement && !['unknown', 'unavailable'].includes(stateObj.state)) {
      stateObj._stateDisplay = stateObj.state + ' ' + stateObj.attributes.unit_of_measurement;
    } else if (domain === 'input_datetime') {
      let date;
      if (!stateObj.attributes.has_time) {
        date = new Date(
          stateObj.attributes.year,
          stateObj.attributes.month - 1,
          stateObj.attributes.day
        );
        stateObj._stateDisplay = formatDate(date, language);
      } else if (!stateObj.attributes.has_date) {
        const now = new Date();
        date = new Date(
          // Due to bugs.chromium.org/p/chromium/issues/detail?id=797548
          // don't use artificial 1970 year.
          now.getFullYear(), now.getMonth(), now.getDay(),
          stateObj.attributes.hour,
          stateObj.attributes.minute
        );
        stateObj._stateDisplay = formatTime(date, language);
      } else {
        date = new Date(
          stateObj.attributes.year, stateObj.attributes.month - 1,
          stateObj.attributes.day, stateObj.attributes.hour,
          stateObj.attributes.minute
        );
        stateObj._stateDisplay = formatDateTime(date, language);
      }
    } else if (domain === 'zwave') {
      if (['initializing', 'dead'].includes(stateObj.state)) {
        stateObj._stateDisplay = localize(`state.zwave.query_stage.${stateObj.state}`, 'query_stage', stateObj.attributes.query_stage);
      } else {
        stateObj._stateDisplay = localize(`state.zwave.default.${stateObj.state}`);
      }
    } else {
      stateObj._stateDisplay = localize(`state.${domain}.${stateObj.state}`);
    }
    // Fall back to default, component backend translation, or raw state if nothing else matches.
    stateObj._stateDisplay = stateObj._stateDisplay
      || localize(`state.default.${stateObj.state}`)
      || localize(`component.${domain}.state.${stateObj.state}`)
      || stateObj.state;
  }

  return stateObj._stateDisplay;
}