feat(utils): 新增 roundTo 保留 n 位小数下的 x 舍 y 入

src/utils/index.ts

@@ -60,6 +60,7 @@ export * from './pMap'
 export * from './readFile'
 export * from './RichUrl'
 export * from './rot13'
+export * from './roundTo'
 export * from './run'
 export * from './sampleBy'
 export * from './sampleIndex'

src/utils/roundTo.test.ts

@@ -0,0 +1,20 @@
+import { roundTo } from './roundTo'
+
+describe('roundTo', () => {
+  test('表现正常', () => {
+    expect(roundTo(5.2)).toBe(5)
+    expect(roundTo(5.25)).toBe(5)
+    expect(roundTo(5.52)).toBe(6)
+    expect(roundTo(5.6)).toBe(6)
+
+    expect(roundTo(5.2, 1)).toBe(5.2)
+    expect(roundTo(5.25, 1)).toBe(5.3)
+    expect(roundTo(5.52, 1)).toBe(5.5)
+    expect(roundTo(5.6, 1)).toBe(5.6)
+
+    expect(roundTo(5.0, 0, 2)).toBe(5)
+    expect(roundTo(5.1, 0, 2)).toBe(5)
+    expect(roundTo(5.2, 0, 2)).toBe(6)
+    expect(roundTo(5.3, 0, 2)).toBe(6)
+  })
+})

src/utils/roundTo.ts

@@ -0,0 +1,18 @@
+import { round } from 'lodash-uni'
+
+/**
+ * 保留 n 位小数下的 x 舍 y 入。
+ *
+ * @param number 数值
+ * @param precision 精度
+ * @param threshold 舍入阈值，等于大于这个值时入，小于这个值时舍
+ */
+export function roundTo(number: number, precision = 0, threshold = 5): number {
+  const [int, decimal] = number.toFixed(precision + 2).split('.')
+  return round(
+    +`${int}.${decimal.slice(0, precision)}${
+      +decimal[precision] >= threshold ? '9' : '0'
+    }`,
+    precision,
+  )
+}