feat(useRound): new function (#1820)

packages/math/useRound/index.md

@@ -0,0 +1,16 @@
+---
+category: '@Math'
+---
+
+# useRound
+
+Reactively Math.round(value).
+
+## Usage
+
+```ts
+import { useRound } from '@vueuse/math'
+
+const value = ref(20.49)
+const result = useRound(value)
+```

packages/math/useRound/index.test.ts

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+import { ref } from 'vue-demi'
+import { useRound } from '.'
+
+describe('useRound', () => {
+  it('should be defined', () => {
+    expect(useRound).toBeDefined()
+  })
+  it('should work', () => {
+    const base = ref(20.49)
+    const result = useRound(base)
+    expect(result.value).toBe(20)
+    base.value = -20.51
+    expect(result.value).toBe(-21)
+  })
+})

packages/math/useRound/index.ts

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+import type { ComputedRef } from 'vue-demi'
+import { computed } from 'vue-demi'
+import type { MaybeComputedRef } from '@vueuse/shared'
+import { resolveUnref } from '@vueuse/shared'
+
+/**
+ * Reactively Math.round(value).
+ *
+ * @see https://vueuse.org/useRound
+ * @param base
+ * @param exponent
+ */
+export function useRound(value: MaybeComputedRef<number>): ComputedRef<number> {
+  return computed<number>(() => Math.round(resolveUnref(value)))
+}