You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.

168 lines
3.8 KiB

This file contains ambiguous Unicode characters!

This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.

let _boundaryCheckingState = true; // 是否进行越界检查的全局开关
/**
* 把错误的数据转正
* @private
* @example strip(0.09999999999999998)=0.1
*/
function strip(num, precision = 15) {
return +parseFloat(Number(num).toPrecision(precision));
}
/**
* Return digits length of a number
* @private
* @param {*number} num Input number
*/
function digitLength(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;
}
/**
* 把小数转成整数,如果是小数则放大成整数
* @private
* @param {*number} num 输入数
*/
function float2Fixed(num) {
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
* @private
* @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} 超出了精度限制,结果可能不正确`);
}
}
}
/**
* 把递归操作扁平迭代化
* @param {number[]} arr 要操作的数字数组
* @param {function} operation 迭代操作
* @private
*/
function iteratorOperation(arr, operation) {
const [num1, num2, ...others] = arr;
let res = operation(num1, num2);
others.forEach((num) => {
res = operation(res, num);
});
return res;
}
/**
* 高精度乘法
* @export
*/
export function times(...nums) {
if (nums.length > 2) {
return iteratorOperation(nums, times);
}
const [num1, num2] = nums;
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);
}
/**
* 高精度加法
* @export
*/
export function plus(...nums) {
if (nums.length > 2) {
return iteratorOperation(nums, plus);
}
const [num1, num2] = nums;
// 取最大的小数位
const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
// 把小数都转为整数然后再计算
return (times(num1, baseNum) + times(num2, baseNum)) / baseNum;
}
/**
* 高精度减法
* @export
*/
export function minus(...nums) {
if (nums.length > 2) {
return iteratorOperation(nums, minus);
}
const [num1, num2] = nums;
const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
return (times(num1, baseNum) - times(num2, baseNum)) / baseNum;
}
/**
* 高精度除法
* @export
*/
export function divide(...nums) {
if (nums.length > 2) {
return iteratorOperation(nums, divide);
}
const [num1, num2] = nums;
const num1Changed = float2Fixed(num1);
const num2Changed = float2Fixed(num2);
checkBoundary(num1Changed);
checkBoundary(num2Changed);
// 重要这里必须用strip进行修正
return times(num1Changed / num2Changed, strip(Math.pow(10, digitLength(num2) - digitLength(num1))));
}
/**
* 四舍五入
* @export
*/
export function round(num, ratio) {
const base = Math.pow(10, ratio);
let result = divide(Math.round(Math.abs(times(num, base))), base);
if (num < 0 && result !== 0) {
result = times(result, -1);
}
// 位数不足则补0
return result;
}
/**
* 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
* @export
*/
export function enableBoundaryChecking(flag = true) {
_boundaryCheckingState = flag;
}
export default {
times,
plus,
minus,
divide,
round,
enableBoundaryChecking,
};