Use browser default time and number formatting with polyfills if needed (#9481)

Co-authored-by: Paulus Schoutsen <balloob@gmail.com>

test/common/string/format_number.ts

@@ -0,0 +1,64 @@
+import { assert } from "chai";
+
+import { formatNumber } from "../../../src/common/number/format_number";
+import {
+  FrontendLocaleData,
+  NumberFormat,
+  TimeFormat,
+} from "../../../src/data/translation";
+
+describe("formatNumber", () => {
+  // Create default to not have to specify a not relevant TimeFormat over and over again.
+  const defaultLocale: FrontendLocaleData = {
+    language: "en",
+    number_format: NumberFormat.language,
+    time_format: TimeFormat.language,
+  };
+
+  // Node only ships with English support for `Intl`, so we can not test for other number formats here.
+  it("Formats English numbers", () => {
+    assert.strictEqual(formatNumber(1234.5, defaultLocale), "1,234.5");
+  });
+
+  it("Test format 'none' (keep dot despite language 'de')", () => {
+    assert.strictEqual(
+      formatNumber(1.23, {
+        ...defaultLocale,
+        language: "de",
+        number_format: NumberFormat.none,
+      }),
+      "1.23"
+    );
+  });
+
+  it("Ensure zero is kept for format 'language'", () => {
+    assert.strictEqual(formatNumber(0, defaultLocale), "0");
+  });
+
+  it("Ensure zero is kept for format 'none'", () => {
+    assert.strictEqual(
+      formatNumber(0, { ...defaultLocale, number_format: NumberFormat.none }),
+      "0"
+    );
+  });
+
+  it("Test empty string input for format 'none'", () => {
+    assert.strictEqual(
+      formatNumber("", { ...defaultLocale, number_format: NumberFormat.none }),
+      ""
+    );
+  });
+
+  it("Test empty string input for format 'language'", () => {
+    assert.strictEqual(formatNumber("", defaultLocale), "0");
+  });
+
+  it("Formats number with options", () => {
+    assert.strictEqual(
+      formatNumber(1234.5, defaultLocale, {
+        minimumFractionDigits: 2,
+      }),
+      "1,234.50"
+    );
+  });
+});