怎么解决javascript数字计算丢失精度问题？

码农天地 - 2020-06-19 08:18:43

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js数字计算丢失精度问题解决方案

计算机世界里，数字的计算，所有语言都会丢失精度，所以没有万全之策，但在人力范围内，尽量解决。

网上找了一部分代码，发现是有问题的，比如:

//加法 Number.prototype.myAdd = function(arg2) { var arg1 = this; if (isNaN(arg2)) { return arg2; } var r1, r2, m; try { r1 = arg1.toString().split(".")[1].length } catch (e) { r1 = 0 } try { r2 = arg2.toString().split(".")[1].length } catch (e) { r2 = 0 } m = Math.pow(10, Math.max(r1, r2)) return (arg1 * m + arg2 * m) / m}//减法 Number.prototype.mySub = function(arg2) { var arg1 = this; if (isNaN(arg2)) { return arg2; } var r1, r2, m, n; try { r1 = arg1.toString().split(".")[1].length } catch (e) { r1 = 0 } try { r2 = arg2.toString().split(".")[1].length } catch (e) { r2 = 0 } m = Math.pow(10, Math.max(r1, r2)); n = (r1 >= r2) ? r1 : r2; return ((arg1 * m - arg2 * m) / m).toFixed(n);}//乘法 Number.prototype.myMul = function(arg2) { var arg1 = this; if (isNaN(arg2)) { return arg2; } var m = 0, s1 = arg1.toString(), s2 = arg2.toString(); try { m += s1.split(".")[1].length } catch (e) {} try { m += s2.split(".")[1].length } catch (e) {} return Number(s1.replace(".", "")) * Number(s2.replace(".", "")) / Math.pow(10, m)}// 除法Number.prototype.myDiv = function(arg2) { var arg1 = this; if (isNaN(arg2)) { return arg2; } var t1 = 0, t2 = 0, r1, r2; try { t1 = arg1.toString().split(".")[1].length } catch (e) {} try { t2 = arg2.toString().split(".")[1].length } catch (e) {} with(Math) { r1 = Number(arg1.toString().replace(".", "")) r2 = Number(arg2.toString().replace(".", "")) return (r1 / r2).myMul(pow(10, t2 - t1)) }}

在计算一些特殊的数字时，仍然有问题：

比如加法：

268.34.myDiv(0.83);//321.7505995203837

所以还要优化

我重新做了一版：

var operationNumber = function (arg1,arg2,operator) { var oper=['+','-','*','/']; // 不合法的运算 if (isNaN(arg1)||isNaN(arg2)||oper.indexOf(operator)<0) { return NaN; } // 除以0 if (operator==='/'&&Number(arg2)===0) { return Infinity; } // 和0相乘 if (operator==='*'&&Number(arg2)===0) { return 0; } // 相等两个数字相减 if ((arg1===arg2||Number(arg1)===Number(arg2))&&operator==='-') { return 0; } var r1, r2, max,_r1,_r2; try { r1 = arg1.toString().split(".")[1].length } catch (e) { r1 = 0 } try { r2 = arg2.toString().split(".")[1].length } catch (e) { r2 = 0 } max = Math.max(r1, r2) _r1 = max-r1; _r2 = max-r2; if (_r1!==0) { arg1=arg1+'0'.repeat(_r1) } if (_r2!==0) { arg2=arg2+'0'.repeat(_r2) } arg1 = Number(arg1.toString().replace('.','')) arg2 = Number(arg2.toString().replace('.','')) var r3 = operator==='*'?(max*2):(operator==='/'?0:max); var newNum = eval(arg1+operator+arg2); if (r3!==0) { var nStr = newNum.toString(); nStr = nStr.replace(/^-/,''); if (nStr.length<r3+1) { nStr = '0'.repeat(r3+1-nStr.length)+nStr; } nStr = nStr.replace(new RegExp('(\\\d{'+r3+'})$'),'.$1'); if (newNum<0) { nStr = '-'+nStr; } newNum = nStr*1; } return newNum;}//加法 Number.prototype.myAdd = function(arg2) { return operationNumber(this,arg2,'+');}//减法 Number.prototype.mySub = function(arg2) { return operationNumber(this,arg2,'-');}//乘法 Number.prototype.myMul = function(arg2) { return operationNumber(this,arg2,'*');}// 除法Number.prototype.myDiv = function(arg2) { return operationNumber(this,arg2,'/');}

如果你发现了bug，评论区及时反馈，我及时跟进修复

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