calculate-asmd - npm Package Compare versions

Comparing version 2.0.0 to 3.0.0

index.js

 "use strict";
 /**
-  加法
-**/
+ * [scaleNum 通过操作其字符串将一个浮点数放大或缩小]
+ * @param  {number} num      要放缩的浮点数
+ * @param  {number} pos      小数点移动位数
+ * pos大于0为放大，小于0为缩小；不传则默认将其变成整数
+ * @return {number}          放缩后的数
+ */
+function scaleNum(num, pos) {
+  if (num === 0 || pos === 0) {
+    return num;
+  }
+
+  let absNum = num;
+  let s = 1;
+  if (num < 0) {
+    absNum = Math.abs(num);
+    s = -1;
+  }
+
+  let parts = absNum.toString().split(".");
+  const intLen = parts[0].length;
+  const decimalLen = parts[1] ? parts[1].length : 0;
+
+  // 默认将其变成整数，放大倍数为原来小数位数
+  if (pos === undefined || pos === null) {
+    return parseFloat(parts[0] + parts[1]);
+  } else if (pos > 0) {
+    // 放大
+    let zeros = pos - decimalLen;
+    while (zeros > 0) {
+      zeros -= 1;
+      parts.push(0);
+    }
+  } else {
+    // 缩小
+    let zeros = Math.abs(pos) - intLen;
+    while (zeros > 0) {
+      zeros -= 1;
+      parts.unshift(0);
+    }
+  }
+
+  const idx = intLen + pos;
+  parts = parts.join("").split("");
+  parts.splice(idx > 0 ? idx : 0, 0, ".");
+
+  if (s < 0) {
+    parts.unshift("-");
+  }
+
+  return parseFloat(parts.join(""));
+}
+
+/**
+ * [add 通过比较两个加数谁的小数位最大，将两数小数点右移为整数进行计算]
+ * @param {number} arg1       加数
+ * @param {number} arg2       被加数
+ * @return {number}           结果
+ */
 function add(arg1, arg2) {
-  var r1 = 0;
-  var r2 = 0;
-  var m = 0;
+  let r1 = 0;
+  let r2 = 0;
+  let scale = 0;
   try {
@@ -21,4 +77,7 @@ r1 = arg1.toString().split(".")[1].length;
 
-  m = Math.pow(10, Math.max(r1, r2));
-  var result = (arg1 * m + arg2 * m) / m;
+  scale = Math.max(r1, r2);
+  const num1 = scaleNum(arg1, scale);
+  const num2 = scaleNum(arg2, scale);
+  const num = num1 + num2;
+  const result = scaleNum(num, -scale);
   return result;
@@ -28,8 +87,11 @@ }
 /**
-  减法
-**/
+ * [sub 通过比较两个加数谁的小数位最大，将两数小数点右移为整数进行计算]
+ * @param {number} arg1       减数
+ * @param {number} arg2       被减数
+ * @return {number}           结果
+ */
 function sub(arg1, arg2) {
-  var r1 = 0;
-  var r2 = 0;
-  var m = 0;
+  let r1 = 0;
+  let r2 = 0;
+  let scale = 0;
   try {
@@ -47,4 +109,7 @@ r1 = arg1.toString().split(".")[1].length;
 
-  m = Math.pow(10, Math.max(r1, r2));
-  var result = (arg1 * m - arg2 * m) / m;
+  scale = Math.max(r1, r2);
+  const num1 = scaleNum(arg1, scale);
+  const num2 = scaleNum(arg2, scale);
+  const num = num1 - num2;
+  const result = scaleNum(num, -scale);
   return result;
@@ -54,53 +119,67 @@ }
 /**
-  乘法
-**/
+ * [mul 将两个浮点数参数replace掉小数点为整数计算，scale在这里进行累计小数位]
+ * @param {number} arg1       乘数
+ * @param {number} arg2       被乘数
+ * @return {number}           结果
+ */
 function mul(arg1, arg2) {
-  var r1 = Number(arg1.toString().replace(".", ""));
-  var r2 = Number(arg2.toString().replace(".", ""));
-  var m = 0;
+  const num1 = Number(arg1.toString().replace(".", ""));
+  const num2 = Number(arg2.toString().replace(".", ""));
+  let scale = 0;
 
   try {
-    m += arg1.toString().split(".")[1].length;
+    scale += arg1.toString().split(".")[1].length;
   } catch (e) {
-    m += 0;
+    scale += 0;
   }
 
   try {
-    m += arg2.toString().split(".")[1].length;
+    scale += arg2.toString().split(".")[1].length;
   } catch (e) {
-    m += 0;
+    scale += 0;
   }
-  var result = (r1 * r2) / Math.pow(10, m);
+
+  const num = num1 * num2;
+  const result = scaleNum(num, -scale);
   return result;
 }
 
-/** 
-    除法
-**/
+/**
+ * [div 将两个浮点数参数replace掉小数点为整数计算，scale是被除数与除数的移动位数差]
+ * @param {number} arg1       除数
+ * @param {number} arg2       被除数
+ * @return {number}           结果
+ */
 function div(arg1, arg2) {
-  var r1 = Number(arg1.toString().replace(".", ""));
-  var r2 = Number(arg2.toString().replace(".", ""));
-  var l1 = 0;
-  var l2 = 0;
+  const num1 = Number(arg1.toString().replace(".", ""));
+  const num2 = Number(arg2.toString().replace(".", ""));
+  let left1 = 0;
+  let left2 = 0;
   try {
-    l1 = Number(arg1.toString().split(".")[1].length);
+    left1 = Number(arg1.toString().split(".")[1].length);
   } catch (e) {
-    l1 = 0;
+    left1 = 0;
   }
 
   try {
-    l2 = Number(arg2.toString().split(".")[1].length);
+    left2 = Number(arg2.toString().split(".")[1].length);
   } catch (e) {
-    l2 = 0;
+    left2 = 0;
   }
 
-  var pow = Math.pow(10, Math.max(l1, l2));
-  //var result =  (Number(r1) / Number(r2)) * Math.pow(10, l2 - l1);  这样也会出现精度问题
+  /**
+   * 当被除数100是整数没有移动小数位，那么left2为0，除数0.57在运算中转整数为57。
+   * 在实际的运算中0.57除以100中的0.57是根据被除数来移动小数的。
+   * 所以，0 - 2 = -2。 将运算结果缩小两位为实际小数点位置
+   *
+   * 除数多拿了被除数的几口口粮，最后要还回去的。
+   *
+   */
+  const scale = left2 - left1;
+  const num = num1 / num2;
 
-  //先把结果放大一定倍数，再去移动相应位数
-  var result = r1 / r2;
-  result = (result * pow * Math.pow(10, l2 - l1)) / pow;
+  const result = scaleNum(num, scale);
   return result;
 }
 
-module.exports = { add, sub, mul, div };
+module.exports = { add, sub, mul, div, scaleNum };

package.json

 {
   "name": "calculate-asmd",
-  "version": "2.0.0",
+  "version": "3.0.0",
   "description": "加减乘除四则运算(calculate/arithmetic)",
@@ -5,0 +5,0 @@ "main": "index.js",

README.md

@@ -7,5 +7,3 @@ # calculate-asmd
 
-1. 浮点数值的最高进度是 17 位小数，但在进行运算的时候其精确度却远远不如整数；整数在进行运算的时候都会转成 10 进制。
-2. Java 和 JavaScript 中计算小数运算时，都会先将十进制的小数换算到对应的二进制，一部分小数并不能完整的换算为二进制，这里就出现了第一次的误差。
-3. 待小数都换算为二进制后，再进行二进制间的运算，得到二进制结果。然后再将二进制结果换算为十进制，这里通常会出现第二次的误差。
+[浮点数运算 0.2 + 0.4 = 0.6 ？](https://github.com/sanshuiwang/Blog/issues/9)
 
@@ -28,24 +26,42 @@ > 使用
 /** 加法 */
-  const addNum = add(9.9, 0.2);
-  console.log("add: ", addNum);
+  const addNum = add(0.2, 0.4);
+  console.log("add(0.2, 0.4): ", addNum);
+  const addNegative = add(0.2, -0.4);
+  console.log("add(0.2, -0.4): ", addNegative);
+  /**
+   *add(0.2, 0.4):  0.6
+   *add(0.2, -0.4):  -0.2
+   */
 
 /** 减法 */
-  const subNum = sub(9.9, 0.2);
-  console.log("sub: ", subNum);
+  const subNum = sub(0.2, 0.4);
+  console.log("sub(0.2, 0.4): ", subNum);
+  const subNegative = sub(0.2, -0.4);
+  console.log("sub(0.2, -0.4): ", subNegative);
+  /**
+   *sub(0.2, 0.4):  -0.2
+   *sub(0.2, -0.4):  0.6
+   */
 
+
 /** 乘法 */
-  const mulNum = mul(9.9, 0.2);
-  console.log("mul: ", mulNum);
+  const mulNum = mul(0.57, 100);
+  console.log("mul(0.57, 100): ", mulNum);
+  const mulNegativ = mul(-0.57, 100);
+  console.log("mul(-0.57, 100): ", mulNegativ);
+  /**
+   *mul(0.57, 100):  57
+   *mul(-0.57, 100):  -57
+   */
 
 /** 除法 */
-  const divNum = div(9.9, 0.2);
-  console.log("div: ", divNum);
+  const divNum = div(0.57, 100);
+  console.log("div(0.57, 100): ", divNum);
+  const divNegative = div(-0.57, 100);
+  console.log("div(-0.57, 100): ", divNegative);
+  /**
+   *div(0.57, 100):  0.0057
+   *div(-0.57, 100):  -0.0057
+   */
 
 ```
-
-> 参考
-
-[精确四则运算](https://blog.csdn.net/u010004317/article/details/79009172)
-
-[js 小数运算出现多位小数如何解决
-](http://www.cnblogs.com/zdz8207/p/js-number-tofixed.html)

test/test.js

@@ -1,12 +0,29 @@
-const { add, sub, mul, div } = require("../index.js");
+const { add, sub, mul, div, scaleNum } = require("../index.js");
 try {
-  const addNum = add(9.9, 0.2);
-  console.log("add: ", addNum);
-  const subNum = sub(9.9, 0.2);
-  console.log("sub: ", subNum);
+  const addNum = add(0.2, 0.4);
+  console.log("add(0.2, 0.4): ", addNum);
+  const addNegative = add(0.2, -0.4);
+  console.log("add(0.2, -0.4): ", addNegative);
 
-  const mulNum = mul(9.9, 0.2);
-  console.log("mul: ", mulNum);
-  const divNum = div(9.9, 0.2);
-  console.log("div: ", divNum);
+  const subNum = sub(0.2, 0.4);
+  console.log("sub(0.2, 0.4): ", subNum);
+  const subNegative = sub(0.2, -0.4);
+  console.log("sub(0.2, -0.4): ", subNegative);
+
+  const mulNum = mul(0.57, 100);
+  console.log("mul(0.57, 100): ", mulNum);
+  const mulNegativ = mul(-0.57, 100);
+  console.log("mul(-0.57, 100): ", mulNegativ);
+
+  const divNum = div(0.57, 100);
+  console.log("div(0.57, 100): ", divNum);
+  const divNegative = div(-0.57, 100);
+  console.log("div(-0.57, 100): ", divNegative);
+
+  console.log("");
+
+  console.log("scaleNum(0.57,2)：", scaleNum(0.57, 2));
+  console.log("scaleNum(-0.57,-2)：", scaleNum(-0.57, -2));
+  console.log("scaleNum(0.57,-2)：", scaleNum(0.57, -2));
+  console.log("scaleNum(-0.57,2)：", scaleNum(-0.57, 2));
 } catch (error) {
@@ -13,0 +30,0 @@ console.error("error: ", error);

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Improved metrics

Total package byte prevSize

8426

increased by101.97%

Number of package files

5

increased by25%

Lines of code

187

increased by81.55%

Number of lines in readme file

66

increased by32%

No dependency changes