change value of number input when pressing arrow up or down

src/event/behavior/keydown.ts

@@ -28,6 +28,10 @@ const keydownBehavior: {
     if (isElementType(target, 'input', {type: 'radio'} as const)) {
       return () => walkRadio(instance, target, 1)
     }
+
+    if (isElementType(target, 'input', {type: 'number'} as const)) {
+      return () => input(instance, target, 'ArrowDown', 'changeNumberInput')
+    }
   },
   ArrowLeft: (event, target, instance) => {
     if (isElementType(target, 'input', {type: 'radio'} as const)) {
@@ -46,6 +50,10 @@ const keydownBehavior: {
     if (isElementType(target, 'input', {type: 'radio'} as const)) {
       return () => walkRadio(instance, target, -1)
     }
+
+    if (isElementType(target, 'input', {type: 'number'} as const)) {
+      return () => input(instance, target, 'ArrowUp', 'changeNumberInput')
+    }
   },
   Backspace: (event, target, instance) => {
     if (isEditable(target)) {

src/event/input.ts

@@ -11,6 +11,8 @@ import {
   EditableInputOrTextarea,
   getMaxLength,
   getNextCursorPosition,
+  isDisabled,
+  isEditable,
   isElementType,
   isValidDateOrTimeValue,
   supportsMaxLength,
@@ -220,6 +222,35 @@ function calculateNewValue(
     }
   }
 
+  if (
+    isElementType(node, 'input', {type: 'number'} as const) &&
+    inputType === 'changeNumberInput' &&
+    !isDisabled(node) &&
+    !node.readOnly
+  ) {
+    const step = node.step ? Number(node.step) : 1
+
+    const reachedMax = value === node.max
+    if (inputData === 'ArrowUp' && !reachedMax) {
+      const exceedsMax = Number(value) + step > Number(node.max)
+      if (exceedsMax && !!node.max) {
+        newValue = node.max
+      } else {
+        newValue = (Number(value) + step).toString()
+      }
+    }
+
+    const reachedMin = value === node.min
+    if (inputData === 'ArrowDown' && !reachedMin) {
+      const exceedsMin = Number(value) - step < Number(node.min)
+      if (exceedsMin && !!node.min) {
+        newValue = node.min
+      } else {
+        newValue = (Number(value) - step).toString()
+      }
+    }
+  }
+
   return {
     oldValue: value,
     newValue,

tests/event/behavior/keydown.ts

@@ -387,3 +387,153 @@ cases(
     },
   },
 )
+
+test("increment number input's value when pressing the arrow up key", () => {
+  const {element} = render<HTMLInputElement>(`<input value="1" type="number"/>`)
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowUp'})
+
+  expect(element).toHaveValue(2)
+})
+
+test("do not increment number input's value when pressing the arrow up key and it would go above the max value", () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="1" type="number" max="1"/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowUp'})
+
+  expect(element).toHaveValue(1)
+})
+
+test("decrement number input's value when pressing the arrow down key", () => {
+  const {element} = render<HTMLInputElement>(`<input value="1" type="number"/>`)
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowDown'})
+
+  expect(element).toHaveValue(0)
+})
+
+test("do not decrement number input's value when pressing the arrow down key and it would go below the min value", () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="1" type="number" min="1"/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowDown'})
+
+  expect(element).toHaveValue(1)
+})
+
+test("increments number input's value by the defined steps when pressing the arrow up key", () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="10" type="number" step="10"/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowUp'})
+
+  expect(element).toHaveValue(20)
+})
+
+test("decrements number input's value by the defined steps when pressing the arrow down key", () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="10" type="number" step="10"/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowDown'})
+
+  expect(element).toHaveValue(0)
+})
+
+test('decrements only to the min value when pressing the arrow down key and steps are too large', async () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="5" type="number" min="0" step="10"/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowDown'})
+
+  expect(element).toHaveValue(0)
+})
+
+test('increments only to the max value when pressing the arrow up key and steps are too large', async () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="5" type="number" max="10" step="10"/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowUp'})
+
+  expect(element).toHaveValue(10)
+})
+
+test("does not increment number input's value when pressing the arrow up key and the input is disabled", () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="1" type="number" disabled/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowUp'})
+
+  expect(element).toHaveValue(1)
+})
+
+test("does not decrement number input's value when pressing the arrow down key and the input is disabled", () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="1" type="number" disabled/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowDown'})
+
+  expect(element).toHaveValue(1)
+})
+
+test("does not increment number input's value when pressing the arrow up key and the input is readonly", () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="1" type="number" readonly/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowUp'})
+
+  expect(element).toHaveValue(1)
+})
+
+test("does not decrement number input's value when pressing the arrow down key and the input is readonly", () => {
+  const {element} = render<HTMLInputElement>(
+    `<input value="1" type="number" readonly/>`,
+  )
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowDown'})
+
+  expect(element).toHaveValue(1)
+})
+
+test('decrements to a negative value when pressing the arrow down key', () => {
+  const {element} = render<HTMLInputElement>(`<input value="0" type="number"/>`)
+
+  const instance = setupInstance()
+
+  instance.dispatchUIEvent(element, 'keydown', {key: 'ArrowDown'})
+
+  expect(element).toHaveValue(-1)
+})