fix(number-input): backspace behavior with formatted numbers (#5719)

* fix(number-input): backspace behavior with formatted numbers

* refactor(number-input): handle locale separator

* fix(number-input): set number input value logic

.changeset/gentle-owls-arrive.md

@@ -0,0 +1,5 @@
+---
+"@heroui/number-input": patch
+---
+
+fix backspace behavior with formatted numbers (#5712)

packages/components/number-input/__tests__/number-input.test.tsx

@@ -621,5 +621,63 @@ describe("NumberInput with React Hook Form", () => {
         await user.keyboard("1234");
       });
     });
+
+    describe("Backspace behavior with formatted numbers", () => {
+      it("should handle backspace when cursor is between first digit and comma", async () => {
+        const {container} = render(
+          <NumberInput
+            defaultValue={1234}
+            formatOptions={{
+              style: "decimal",
+              useGrouping: true,
+            }}
+            label="test number input"
+          />,
+        );
+
+        const input = container.querySelector("input[type='text']") as HTMLInputElement;
+
+        expect(input.value).toBe("1,234");
+
+        act(() => {
+          input.focus();
+          input.setSelectionRange(1, 1);
+        });
+
+        act(() => {
+          fireEvent.keyDown(input, {key: "Backspace", code: "Backspace"});
+        });
+
+        expect(input.value).toBe("234");
+      });
+
+      it("should handle backspace for other formatted number scenarios", async () => {
+        const {container} = render(
+          <NumberInput
+            defaultValue={1234567}
+            formatOptions={{
+              style: "decimal",
+              useGrouping: true,
+            }}
+            label="test number input"
+          />,
+        );
+
+        const input = container.querySelector("input[type='text']") as HTMLInputElement;
+
+        expect(input.value).toBe("1,234,567");
+
+        act(() => {
+          input.focus();
+          input.setSelectionRange(5, 5);
+        });
+
+        act(() => {
+          fireEvent.keyDown(input, {key: "Backspace", code: "Backspace"});
+        });
+
+        expect(input.value).toBe("123,567");
+      });
+    });
   });
 });

packages/components/number-input/src/use-number-input.ts

@@ -242,7 +242,48 @@ export function useNumberInput(originalProps: UseNumberInputProps) {
 
   const handleKeyDown = useCallback(
     (e: React.KeyboardEvent<HTMLInputElement>) => {
+      const inputElement = e.currentTarget;
+      const {selectionStart, selectionEnd, value} = inputElement;
+      // locale-aware grouping separator
+      const nf = new Intl.NumberFormat(locale, {useGrouping: true});
+      const groupChar = nf.formatToParts(1000).find((p) => p.type === "group")?.value ?? ",";
+
+      // handle backspace when cursor is between a digit and the first group separator
+      // e.g. 1|,234 (en-US) or 1|.234 (de-DE) -> backspace removes the preceding digit if (
       if (
+        e.key === "Backspace" &&
+        !originalProps.isReadOnly &&
+        !originalProps.isDisabled &&
+        selectionStart !== null &&
+        selectionEnd !== null &&
+        selectionStart === selectionEnd &&
+        selectionStart > 0 &&
+        value[selectionStart] === groupChar &&
+        value[selectionStart - 1] !== groupChar
+      ) {
+        e.preventDefault();
+        // e.g. 1,234 -> ,234
+        const newValue = value.slice(0, selectionStart - 1) + value.slice(selectionStart);
+        // e.g. ,234 -> 234
+        const cleanValue = newValue.replace(/[^\d.-]/g, "");
+
+        if (cleanValue === "" || cleanValue === "-") {
+          state.setInputValue("");
+        } else {
+          const numberValue = parseFloat(cleanValue);
+
+          if (!isNaN(numberValue)) {
+            state.setNumberValue(numberValue);
+          }
+        }
+
+        setTimeout(() => {
+          // set the new cursor position
+          const pos = Math.max(0, selectionStart - 1);
+
+          inputElement.setSelectionRange(pos, pos);
+        }, 0);
+      } else if (
         e.key === "Escape" &&
         inputValue &&
         (isClearable || onClear) &&
@@ -252,7 +293,7 @@ export function useNumberInput(originalProps: UseNumberInputProps) {
         onClear?.();
       }
     },
-    [inputValue, state.setInputValue, onClear, isClearable, originalProps.isReadOnly],
+    [inputValue, state, onClear, isClearable, originalProps.isReadOnly],
   );
 
   const getBaseProps: PropGetter = useCallback(