Formats number state with selected language in compute_state_display

src/common/entity/compute_state_display.ts

@@ -5,6 +5,7 @@ import { formatDateTime } from "../datetime/format_date_time";
 import { formatTime } from "../datetime/format_time";
 import { LocalizeFunc } from "../translations/localize";
 import { computeStateDomain } from "./compute_state_domain";
+import { numberFormat } from "../string/number-format";
 
 export const computeStateDisplay = (
   localize: LocalizeFunc,
@@ -19,7 +20,9 @@ export const computeStateDisplay = (
   }
 
   if (stateObj.attributes.unit_of_measurement) {
-    return `${compareState} ${stateObj.attributes.unit_of_measurement}`;
+    return `${numberFormat(compareState, language)} ${
+      stateObj.attributes.unit_of_measurement
+    }`;
   }
 
   const domain = computeStateDomain(stateObj);

src/common/string/number-format.ts

@@ -0,0 +1,22 @@
+/**
+ * Formats a number based on the specified language with thousands separator(s) and decimal character for better legibility.
+ *
+ * @param num The number to format
+ * @param language The language to use when formatting the number
+ */
+export const numberFormat = (
+  num: string | number,
+  language: string
+): string => {
+  // Polyfill for Number.isNaN, which is more reliable that the global isNaN()
+  Number.isNaN =
+    Number.isNaN ||
+    function isNaN(input) {
+      return typeof input === "number" && isNaN(input);
+    };
+
+  if (!Number.isNaN(Number(num)) && Intl) {
+    return new Intl.NumberFormat(language).format(Number(num));
+  }
+  return num.toString();
+};

test-mocha/common/entity/compute_state_display.ts

@@ -64,6 +64,20 @@ describe("computeStateDisplay", () => {
     assert.strictEqual(computeStateDisplay(localize, stateObj, "en"), "123 m");
   });
 
+  it("Localizes and formats numeric sensor value with units", () => {
+    const stateObj: any = {
+      entity_id: "sensor.test",
+      state: "1234.5",
+      attributes: {
+        unit_of_measurement: "m",
+      },
+    };
+    assert.strictEqual(
+      computeStateDisplay(localize, stateObj, "en"),
+      "1,234.5 m"
+    );
+  });
+
   it("Localizes unknown sensor value with units", () => {
     const altLocalize = (message, ...args) => {
       if (message === "state.sensor.unknown") {