【转】JS中处理Number浮点数精度问题
https://github.com/dt-fe/number-precision
~(function(root, factory) {
if (typeof define === "function" && define.amd) {
define([], factory);
} else if (typeof module === "object" && module.exports) {
module.exports = factory();
} else {
root.NP = factory();
}
}(this, function() {
'use strict';
/**
* @ file 解决浮动运算问题，避免小数点后产生多位数和计算精度损失。
* 问题示例：2.3 + 2.4 = 4.699999999999999，1.0 - 0.9 = 0.09999999999999998
*/
return {
/**
* 把错误的数据转正
* strip(0.09999999999999998)=0.1
*/
strip: function (num, precision = 12) {
return +parseFloat(num.toPrecision(precision));
},
/**
* Return digits length of a number
* @ param {*number} num Input number
*/
digitLength: function (num) {
// Get digit length of e
const eSplit = num.toString().split(/[eE]/);
const len = (eSplit[0].split('.')[1] || '').length - (+(eSplit[1] || 0));
return len > 0 ? len : 0;
},
/**
* 精确加法
*/
plus: function (num1, num2) {
const baseNum = Math.pow(10, Math.max(this.digitLength(num1), this.digitLength(num2)));
return (num1 * baseNum + num2 * baseNum) / baseNum;
},
/**
* 精确减法
*/
minus: function (num1, num2) {
const baseNum = Math.pow(10, Math.max(this.digitLength(num1), this.digitLength(num2)));
return (num1 * baseNum - num2 * baseNum) / baseNum;
},
/**
* 精确乘法
*/
times: function (num1, num2) {
const num1Changed = Number(num1.toString().replace('.', ''));
const num2Changed = Number(num2.toString().replace('.', ''));
const baseNum = this.digitLength(num1) + this.digitLength(num2);
return num1Changed * num2Changed / Math.pow(10, baseNum);
},
/**
* 精确除法
*/
divide: function (num1, num2) {
const num1Changed = Number(num1.toString().replace('.', ''));
const num2Changed = Number(num2.toString().replace('.', ''));
return this.times((num1Changed / num2Changed), Math.pow(10, this.digitLength(num2) - this.digitLength(num1)));
},
/**
* 四舍五入
*/
round: function (num, ratio) {
const base = Math.pow(10, ratio);
return this.divide(Math.round(this.times(num, base)), base);
}
};
}));
方法：
NP.strip(num) // strip a number to nearest right number NP.plus(num1, num2) // addition, num + num2 NP.minus(num1, num2) // subtraction, num1 - num2 NP.times(num1, num2) // multiplication, num1 * num2 NP.divide(num1, num2) // division, num1 / num2 NP.round(num, ratio) // round a number based on ratio
使用：
NP.strip(0.09999999999999998); // =0.1
NP.plus(0.1, 0.2); // =0.3 not 0.30000000000000004
NP.plus(2.3, 2.4); // =4.7 not 4.699999999999999
NP.minus(1.0, 0.9); // =0.1 not 0.09999999999999998
NP.times(3, 0.3); // =0.9 not 0.8999999999999999
NP.times(0.362, 100); // = 36.2, not 36.199999999999996
NP.divide(1.21, 1.1); // =1.1 not 1.0999999999999999
NP.round(0.105, 2); // =0.11 not 0.1
