type numType = number | string;
/**
* @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: numType, precision = 15): number {
return +parseFloat(Number(num).toPrecision(precision));
}
/**
* Return digits length of a number
* @param {*number} num Input number
*/
function digitLength(num: numType): number {
// 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;
}
/**
* 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: numType): number {
if (num.toString().indexOf('e') === -1) {
return Number(num.toString().replace('.', ''));
}
const 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: number) {
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: numType, num2: numType, ...others: numType[]): number {
if (others.length > 0) {
return times(times(num1, num2), others[0], ...others.slice(1));
}
const num1Changed = float2Fixed(num1);
const num2Changed = float2Fixed(num2);
const baseNum = digitLength(num1) + digitLength(num2);
const leftValue = num1Changed * num2Changed;
checkBoundary(leftValue);
return leftValue / Math.pow(10, baseNum);
}
/**
* 精确加法
*/
function plus(num1: numType, num2: numType, ...others: numType[]): number {
if (others.length > 0) {
return plus(plus(num1, num2), others[0], ...others.slice(1));
}
const 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: numType, num2: numType, ...others: numType[]): number {
if (others.length > 0) {
return minus(minus(num1, num2), others[0], ...others.slice(1));
}
const 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: numType, num2: numType, ...others: numType[]): number {
if (others.length > 0) {
return divide(divide(num1, num2), others[0], ...others.slice(1));
}
const num1Changed = float2Fixed(num1);
const 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: numType, ratio: number): number {
const base = Math.pow(10, ratio);
return divide(Math.round(times(num, base)), base);
}
let _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
*/
// 这里可以设置边界检查（默认是true）
function enableBoundaryChecking(flag = true) {
_boundaryCheckingState = flag;
}
// 输出上面的方法
export { strip, plus, minus, times, divide, round, digitLength, float2Fixed, enableBoundaryChecking };
export default {
strip,
plus,
minus,
times,
divide,
round,
digitLength,
float2Fixed,
enableBoundaryChecking,
};
