计算精度问题通常发生在浮点数运算中，由于浮点数的表示所限，可能导致精度损失。
// 比如
0.1 + 0.2 // 结果为 0.30000000000000004
0.3 - 0.1 // 结果为 0.19999999999999996
vue 使用decimal.js 解决小数相加合计精确度丢失问题
'use strict';
Object.defineProperty(exports, '__esModule', {
value: true
});
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user ，medthor
NP.strip(num) // strip a number to nearest right number
NP.plus(num1, num2, num3, ...) // addition, num + num2 + num3, two numbers is required at least.
NP.minus(num1, num2, num3, ...) // subtraction, num1 - num2 - num3
NP.times(num1, num2, num3, ...) // multiplication, num1 * num2 * num3
NP.divide(num1, num2, num3, ...) // division, num1 / num2 / num3
NP.round(num, ratio) // round a number based on ratio
***************************************************************************** /
/ global Reflect, Promise */
function __spreadArrays() {
for (var s = 0, i = 0, il = arguments.length; i < il; i++) s += arguments[i].length;
for (var r = Array(s), k = 0, i = 0; i < il; i++)
for (var a = arguments[i], j = 0, jl = a.length; j < jl; j++, k++)
r[k] = a[j];
return r;
}
/**
@desc 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
**/
/**
把错误的数据转正
strip(0.09999999999999998)=0.1
*/
function strip(num, precision) {
if (precision === void 0) {
precision = 15;
}
return +parseFloat(Number(num).toPrecision(precision));
}
/**
Return digits length of a number
@param {number} num Input number
*/
function digitLength(num) {
// Get digit length of e
var eSplit = num.toString().split(/[eE]/);
var len = (eSplit[0].split('.')[1] || '').length - +(eSplit[1] || 0);
return len > 0 ? len : 0;
}
/**
把小数转成整数，支持科学计数法。如果是小数则放大成整数
@param {number} num 输入数
*/
function float2Fixed(num) {
if (num.toString().indexOf('e') === -1) {
return Number(num.toString().replace('.', ''));
}
var dLen = digitLength(num);
return dLen > 0 ? strip(Number(num) * Math.pow(10, dLen)) : Number(num);
}
/**
检测数字是否越界，如果越界给出提示
@param {number} num 输入数
*/
function checkBoundary(num) {
if (_boundaryCheckingState) {
if (num > Number.MAX_SAFE_INTEGER || num < Number.MIN_SAFE_INTEGER) {
console.warn(num + " is beyond boundary when transfer to integer, the results may not be accurate");
}
}
}
/**
精确乘法
*/
function times(num1, num2) {
var others = [];
for (var _i = 2; _i < arguments.length; _i++) {
others[_i - 2] = arguments[_i];
}
if (others.length > 0) {
return times.apply(void 0, __spreadArrays([times(num1, num2), others[0]], others.slice(1)));
}
var num1Changed = float2Fixed(num1);
var num2Changed = float2Fixed(num2);
var baseNum = digitLength(num1) + digitLength(num2);
var leftValue = num1Changed * num2Changed;
checkBoundary(leftValue);
return leftValue / Math.pow(10, baseNum);
}
/**
精确加法
*/
function plus(num1, num2) {
var others = [];
for (var _i = 2; _i < arguments.length; _i++) {
others[_i - 2] = arguments[_i];
}
if (others.length > 0) {
return plus.apply(void 0, __spreadArrays([plus(num1, num2), others[0]], others.slice(1)));
}
var baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
return (times(num1, baseNum) + times(num2, baseNum)) / baseNum;
}
/**
精确减法
*/
function minus(num1, num2) {
var others = [];
for (var _i = 2; _i < arguments.length; _i++) {
others[_i - 2] = arguments[_i];
}
if (others.length > 0) {
return minus.apply(void 0, __spreadArrays([minus(num1, num2), others[0]], others.slice(1)));
}
var baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
return (times(num1, baseNum) - times(num2, baseNum)) / baseNum;
}
/**
精确除法
*/
function divide(num1, num2) {
var others = [];
for (var _i = 2; _i < arguments.length; _i++) {
others[_i - 2] = arguments[_i];
}
if (others.length > 0) {
return divide.apply(void 0, __spreadArrays([divide(num1, num2), others[0]], others.slice(1)));
}
var num1Changed = float2Fixed(num1);
var num2Changed = float2Fixed(num2);
checkBoundary(num1Changed);
checkBoundary(num2Changed);
// fix: 类似 10 ** -4 为 0.00009999999999999999，strip 修正
return times(num1Changed / num2Changed, strip(Math.pow(10, digitLength(num2) - digitLength(num1))));
}
/**
四舍五入
*/
function round(num, ratio) {
var base = Math.pow(10, ratio);
return divide(Math.round(times(num, base)), base);
}
var _boundaryCheckingState = true;
/*
是否进行边界检查，默认开启
@param flag 标记开关，true 为开启，false 为关闭，默认为 true
*/
function enableBoundaryChecking(flag) {
if (flag === void 0) {
flag = true;
}
_boundaryCheckingState = flag;
}
var index = {
strip: strip,
plus: plus,
minus: minus,
times: times,
divide: divide,
round: round,
digitLength: digitLength,
float2Fixed: float2Fixed,
enableBoundaryChecking: enableBoundaryChecking,
};
exports.strip = strip;
exports.plus = plus;
exports.minus = minus;
exports.times = times;
exports.divide = divide;
exports.round = round;
exports.digitLength = digitLength;
exports.float2Fixed = float2Fixed;
exports.enableBoundaryChecking = enableBoundaryChecking;
exports['default'] = index;
var commonFunc= require('../../utils/commonFunc');
Page({
onload() {
commonFunc.minus(0.2, 0.1)
}
})