正常情况下0.0023 * 100 = 0.23,但js运算会出现下面这种精度丢失问题:
0.0023 - 0.00000011 ==> 0.0022998899999999997 0.0023 + 0.00000000000001 ==> 0.0023000000000099998 0.0023 * 100 ==> 0.22999999999999998 0.0023 / 0.00001 ==> 229.99999999999997
实际打印结果:
取余也同样存在精度丢失问题:
下面直接参考别人写的方法:【中间处理了一些问题,文章最后有整理优化后的运算方法 + 取余的精度方法】
// 加 function floatAdd(arg1, 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 (floatMultiply(arg1 , m) + floatMultiply(arg2 , m)) / m; } // 减 function floatSub(arg1, 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)); // 动态控制精度长度 n = (r1 >= r2) ? r1 : r2; return ((floatMultiply(arg1 , m) - floatMultiply(arg2 , m)) / m).toFixed(n); } // 乘 function floatMultiply(arg1, arg2) { if(arg1 == null || arg2 == null){ return null; } var n1,n2; var r1, r2; // 小数位数 try { r1 = arg1.toString().split(".")[1].length; } catch (e) { r1 = 0; } try { r2 = arg2.toString().split(".")[1].length; } catch (e) { r2 = 0; } n1 = Number(arg1.toString().replace(".", "")); n2 = Number(arg2.toString().replace(".", "")); return n1 * n2 / Math.pow(10, r1+r2); } // 除 function floatDivide(arg1, arg2) { if(arg1 == null){ return null; } if(arg2 == null || arg2 == 0){ return null; } var n1,n2; var r1, r2; // 小数位数 try { r1 = arg1.toString().split(".")[1].length; } catch (e) { r1 = 0; } try { r2 = arg2.toString().split(".")[1].length; } catch (e) { r2 = 0; } n1 = Number(arg1.toString().replace(".", "")); n2 = Number(arg2.toString().replace(".", "")); return (n1 / n2) * Math.pow(10, r2 - r1); }
上面运算方法存在的问题:
1、floatDivide( 0.0033 , 100 ) = 0.000032999999999999996结果出现精度丢失问题:
解决:除法运算的最后,需要使用乘法的方法,而不能直接相乘:
2、floatDivide( 170890000 , 380026238.96999997 ) 得到的结果和实际数出入很大,如下图:
测试:
由上面两种情况猜测是乘法里面的科学计数法的问题:
解决:添加将科学计数法转为字符串的方法,得到的结果就正常了,看下图:
下面是测试的代码:
var toNonExponential = (num)=> { var m = num.toExponential().match(/\d(?:\.(\d*))?e([+-]\d+)/); return num.toFixed(Math.max(0, (m[1] || '').length - m[2])); } /** * 乘法 - js运算精度丢失问题 * @param arg1 数1 * @param arg2 数2 */ var floatMultiply = (arg1, arg2) => { if (arg1 == null || arg2 == null) { return null; } arg1 = toNonExponential(arg1); arg2 = toNonExponential(arg2); var n1, n2; var r1, r2; // 小数位数 try { r1 = arg1.toString().split(".")[1].length; } catch (e) { r1 = 0; } try { r2 = arg2.toString().split(".")[1].length; } catch (e) { r2 = 0; } n1 = Number(arg1.toString().replace(".", "")); n2 = Number(arg2.toString().replace(".", "")); return n1 * n2 / Math.pow(10, r1 + r2); }var floatDivide = (arg1, arg2) => { if (arg1 == null) { return null; } if (arg2 == null || arg2 == 0) { return null; } var n1, n2; var r1, r2; // 小数位数 try { r1 = arg1.toString().split(".")[1].length; } catch (e) { r1 = 0; } try { r2 = arg2.toString().split(".")[1].length; } catch (e) { r2 = 0; } n1 = Number(arg1.toString().replace(".", "")); n2 = Number(arg2.toString().replace(".", "")); return floatMultiply((n1 / n2), Math.pow(10, r2 - r1)); // return (n1 / n2) * Math.pow(10, r2 - r1); // 直接乘法还是会出现精度问题 } console.log(floatMultiply(4.496794759834739e-9,100000000)); // console.log( floatDivide(170890000,380026238.9699997) ); // console.log( floatDivide(170890000,380026238.969999) ); // console.log( floatDivide(170890000,380026238.96999) );
优化后的运算方法整合:
/** * 将科学计数法的数字转为字符串 * 说明:运算精度丢失方法中处理数字的时候,如果出现科学计数法,就会导致结果出错 * 4.496794759834739e-9 ==> 0.000000004496794759834739 * 4.496794759834739e+9 ==> 4496794759.834739 * @param num */ var toNonExponential = (num)=> { if(num == null) { return num; } if(typeof num == "number") { var m = num.toExponential().match(/\d(?:\.(\d*))?e([+-]\d+)/); return num.toFixed(Math.max(0, (m[1] || '').length - m[2])); }else { return num; } } /** * 乘法 - js运算精度丢失问题 * @param arg1 数1 * @param arg2 数2 * 0.0023 * 100 ==> 0.22999999999999998 * {{ 0.0023 | multiply(100) }} ==> 0.23 */ var floatMultiply = (arg1, arg2) => { arg1 = Number(arg1); arg2 = Number(arg2); if ((!arg1 && arg1!==0) || (!arg2 && arg2!==0)) { return null; } arg1 = toNonExponential(arg1); arg2 = toNonExponential(arg2); var n1, n2; var r1, r2; // 小数位数 try { r1 = arg1.toString().split(".")[1].length; } catch (e) { r1 = 0; } try { r2 = arg2.toString().split(".")[1].length; } catch (e) { r2 = 0; } n1 = Number(arg1.toString().replace(".", "")); n2 = Number(arg2.toString().replace(".", "")); return n1 * n2 / Math.pow(10, r1 + r2); } /** * 除法 - js运算精度丢失问题 * @param arg1 数1 * @param arg2 数2 * 0.0023 / 0.00001 ==> 229.99999999999997 * {{ 0.0023 | divide(0.00001) }} ==> 230 */ var floatDivide = (arg1, arg2) => { arg1 = Number(arg1); arg2 = Number(arg2); if (!arg2) { return null; } if (!arg1 && arg1!==0) { return null; }else if(arg1===0) { return 0; } arg1 = toNonExponential(arg1); arg2 = toNonExponential(arg2); var n1, n2; var r1, r2; // 小数位数 try { r1 = arg1.toString().split(".")[1].length; } catch (e) { r1 = 0; } try { r2 = arg2.toString().split(".")[1].length; } catch (e) { r2 = 0; } n1 = Number(arg1.toString().replace(".", "")); n2 = Number(arg2.toString().replace(".", "")); return floatMultiply((n1 / n2), Math.pow(10, r2 - r1)); // return (n1 / n2) * Math.pow(10, r2 - r1); // 直接乘法还是会出现精度问题 } /** * 加法 - js运算精度丢失问题 * @param arg1 数1 * @param arg2 数2 * 0.0023 + 0.00000000000001 ==> 0.0023000000000099998 * {{ 0.0023 | plus(0.00000000000001) }} ==> 0.00230000000001 */ var floatAdd = (arg1, arg2) => { arg1 = Number(arg1) || 0; arg2 = Number(arg2) || 0; arg1 = toNonExponential(arg1); arg2 = toNonExponential(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 (floatMultiply(arg1, m) + floatMultiply(arg2, m)) / m; } /** * 减法 - js运算精度丢失问题 * @param arg1 数1 * @param arg2 数2 * 0.0023 - 0.00000011 ==> 0.0022998899999999997 * {{ 0.0023 | minus( 0.00000011 ) }} ==> 0.00229989 */ var floatSub = (arg1, arg2) => { arg1 = Number(arg1) || 0; arg2 = Number(arg2) || 0; arg1 = toNonExponential(arg1); arg2 = toNonExponential(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)); // 动态控制精度长度 n = (r1 >= r2) ? r1 : r2; return ((floatMultiply(arg1, m) - floatMultiply(arg2, m)) / m).toFixed(n); } /** * 取余 - js运算精度丢失问题 * @param arg1 数1 * @param arg2 数2 * 12.24 % 12 ==> 0.2400000000000002 * {{ 12.24 | mod( -12 ) }} ==> 0.24 */ var floatMod = (arg1, arg2) => { arg1 = Number(arg1); arg2 = Number(arg2); if (!arg2) { return null; } if (!arg1 && arg1!==0) { return null; }else if(arg1===0) { return 0; } let intNum = arg1 / arg2; intNum = intNum < 0 ? Math.ceil( arg1 / arg2 ) : Math.floor( arg1 / arg2 ); // -1.02 取整为 -1; 1.02取整为1 let intVal = floatMultiply(intNum, arg2); return floatSub( arg1,intVal ); 12.4 }