feat(Calculator): 可通过 make 创建新的计算器

fjc0k · Feb 12, 2022 · cf1a02b · cf1a02b
1 parent 5e6e393
commit cf1a02b
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Showing 4 changed files with 109 additions and 49 deletions.
diff --git a/package.json b/package.json
@@ -120,7 +120,7 @@
     "cli-table3": "^0.6.0",
     "cuid": "^2.1.8",
     "date-fns": "^2.24.0",
-    "decimal.js": "^10.3.1",
+    "decimal.js-light": "^2.5.1",
     "fast-xml-parser": "^3.18.0",
     "ioredis": "^4.22.0",
     "lodash-uni": "^1.1.0",

diff --git a/src/utils/Calculator.test.ts b/src/utils/Calculator.test.ts
@@ -75,4 +75,23 @@ describe('Calculator', () => {
       expect(Calculator.div(0.69, 10)).toBe(0.069)
     })
   })
+
+  describe('银行家舍入法', () => {
+    // https://baike.baidu.com/item/%E9%93%B6%E8%A1%8C%E5%AE%B6%E8%88%8D%E5%85%A5/4781630?fr=aladdin
+    test('ok', () => {
+      expect(Calculator.make({ decimalPlaces: 2 }).add(9, 0.825)).toBe(9.83)
+      expect(
+        Calculator.make({
+          decimalPlaces: 2,
+          rounding: Calculator.decimal.ROUND_HALF_EVEN,
+        }).add(9, 0.825),
+      ).toBe(9.82)
+      expect(
+        Calculator.make({
+          decimalPlaces: 2,
+          rounding: Calculator.decimal.ROUND_HALF_EVEN,
+        }).add(9, 0.82501),
+      ).toBe(9.83)
+    })
+  })
 })
diff --git a/src/utils/Calculator.ts b/src/utils/Calculator.ts
@@ -1,9 +1,20 @@
-import Decimal from 'decimal.js'
+import DecimalLight, { Config } from 'decimal.js-light'
 
-/**
- * 科学计算器。主要是为了避免 js 的浮点数精度计算问题。
- */
-export class Calculator {
+export interface CalculatorInstance {
+  /**
+   * decimal.js 引用。
+   */
+  decimal: typeof DecimalLight
+  /**
+   * 根据配置创建一个新的计算器。
+   *
+   * @param config 配置
+   */
+  make(
+    config?: Config & {
+      decimalPlaces?: number
+    },
+  ): CalculatorInstance
   /**
    * 加。
    *
@@ -12,14 +23,7 @@ export class Calculator {
    *
    * @param values 加数列表
    */
-  static add(...values: number[]): number {
-    return values.length === 0
-      ? 0
-      : values.length === 1
-      ? values[0]
-      : values.reduce((res, value) => res.add(value), new Decimal(0)).toNumber()
-  }
-
+  add(...values: number[]): number
   /**
    * 减。
    *
@@ -28,20 +32,7 @@ export class Calculator {
    *
    * @param values 减数列表
    */
-  static sub(...values: number[]): number {
-    return values.length === 0
-      ? 0
-      : values.length === 1
-      ? values[0]
-      : values
-          .reduce(
-            (res, value, index) =>
-              index === 0 ? res.add(value) : res.sub(value),
-            new Decimal(0),
-          )
-          .toNumber()
-  }
-
+  sub(...values: number[]): number
   /**
    * 乘。
    *
@@ -50,14 +41,7 @@ export class Calculator {
    *
    * @param values 乘数列表
    */
-  static mul(...values: number[]): number {
-    return values.length === 0
-      ? 0
-      : values.length === 1
-      ? values[0]
-      : values.reduce((res, value) => res.mul(value), new Decimal(1)).toNumber()
-  }
-
+  mul(...values: number[]): number
   /**
    * 除。
    *
@@ -66,17 +50,69 @@ export class Calculator {
    *
    * @param values 除数列表
    */
-  static div(...values: number[]): number {
-    return values.length === 0
-      ? 0
-      : values.length === 1
-      ? values[0]
-      : values
-          .reduce(
-            (res, value, index) =>
-              index === 0 ? res.add(value) : res.div(value),
-            new Decimal(0),
-          )
-          .toNumber()
+  div(...values: number[]): number
+}
+
+const make: CalculatorInstance['make'] = config => {
+  const Decimal = DecimalLight.clone(config)
+
+  const Calculator: CalculatorInstance = {
+    decimal: DecimalLight,
+    make: make,
+    add(...values) {
+      return values.length === 0
+        ? 0
+        : values.length === 1
+        ? values[0]
+        : values
+            .reduce((res, value) => res.add(value), new Decimal(0))
+            .toDecimalPlaces(config?.decimalPlaces)
+            .toNumber()
+    },
+    sub(...values) {
+      return values.length === 0
+        ? 0
+        : values.length === 1
+        ? values[0]
+        : values
+            .reduce(
+              (res, value, index) =>
+                index === 0 ? res.add(value) : res.sub(value),
+              new Decimal(0),
+            )
+            .toDecimalPlaces(config?.decimalPlaces)
+            .toNumber()
+    },
+    mul(...values) {
+      return values.length === 0
+        ? 0
+        : values.length === 1
+        ? values[0]
+        : values
+            .reduce((res, value) => res.mul(value), new Decimal(1))
+            .toDecimalPlaces(config?.decimalPlaces)
+            .toNumber()
+    },
+    div(...values) {
+      return values.length === 0
+        ? 0
+        : values.length === 1
+        ? values[0]
+        : values
+            .reduce(
+              (res, value, index) =>
+                index === 0 ? res.add(value) : res.div(value),
+              new Decimal(0),
+            )
+            .toDecimalPlaces(config?.decimalPlaces)
+            .toNumber()
+    },
   }
+
+  return Calculator
 }
+
+/**
+ * 科学计算器。主要是为了避免 js 的浮点数精度计算问题。
+ */
+export const Calculator = make()
diff --git a/yarn.lock b/yarn.lock
@@ -3444,7 +3444,12 @@ decamelize@^1.1.0, decamelize@^1.2.0:
   resolved "https://registry.npm.taobao.org/decamelize/download/decamelize-1.2.0.tgz?cache=0&sync_timestamp=1610348726858&other_urls=https%3A%2F%2Fregistry.npm.taobao.org%2Fdecamelize%2Fdownload%2Fdecamelize-1.2.0.tgz#f6534d15148269b20352e7bee26f501f9a191290"
   integrity sha1-9lNNFRSCabIDUue+4m9QH5oZEpA=
 
-decimal.js@^10.2.1, decimal.js@^10.3.1:
+decimal.js-light@^2.5.1:
+  version "2.5.1"
+  resolved "https://registry.npmmirror.com/decimal.js-light/-/decimal.js-light-2.5.1.tgz#134fd32508f19e208f4fb2f8dac0d2626a867934"
+  integrity sha512-qIMFpTMZmny+MMIitAB6D7iVPEorVw6YQRWkvarTkT4tBeSLLiHzcwj6q0MmYSFCiVpiqPJTJEYIrpcPzVEIvg==
+
+decimal.js@^10.2.1:
   version "10.3.1"
   resolved "https://registry.npmmirror.com/decimal.js/download/decimal.js-10.3.1.tgz#d8c3a444a9c6774ba60ca6ad7261c3a94fd5e783"
   integrity sha512-V0pfhfr8suzyPGOx3nmq4aHqabehUZn6Ch9kyFpV79TGDTWFmHqUqXdabR7QHqxzrYolF4+tVmJhUG4OURg5dQ==