169 lines
3.8 KiB
JavaScript
169 lines
3.8 KiB
JavaScript
let _boundaryCheckingState = true; // 是否进行越界检查的全局开关
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/**
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* 把错误的数据转正
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* @private
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* @example strip(0.09999999999999998)=0.1
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*/
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function strip(num, precision = 15) {
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return +parseFloat(Number(num).toPrecision(precision));
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}
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/**
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* Return digits length of a number
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* @private
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* @param {*number} num Input number
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*/
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function digitLength(num) {
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// Get digit length of e
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const eSplit = num.toString().split(/[eE]/);
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const len = (eSplit[0].split('.')[1] || '').length - +(eSplit[1] || 0);
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return len > 0 ? len : 0;
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}
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/**
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* 把小数转成整数,如果是小数则放大成整数
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* @private
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* @param {*number} num 输入数
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*/
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function float2Fixed(num) {
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if (num.toString().indexOf('e') === -1) {
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return Number(num.toString().replace('.', ''));
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}
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const dLen = digitLength(num);
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return dLen > 0 ? strip(Number(num) * Math.pow(10, dLen)) : Number(num);
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}
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/**
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* 检测数字是否越界，如果越界给出提示
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* @private
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* @param {*number} num 输入数
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*/
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function checkBoundary(num) {
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if (_boundaryCheckingState) {
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if (num > Number.MAX_SAFE_INTEGER || num < Number.MIN_SAFE_INTEGER) {
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console.warn(`${num} 超出了精度限制，结果可能不正确`);
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}
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}
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}
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/**
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* 把递归操作扁平迭代化
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* @param {number[]} arr 要操作的数字数组
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* @param {function} operation 迭代操作
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* @private
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*/
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function iteratorOperation(arr, operation) {
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const [num1, num2, ...others] = arr;
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let res = operation(num1, num2);
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others.forEach((num) => {
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res = operation(res, num);
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});
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return res;
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}
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/**
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* 高精度乘法
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* @export
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*/
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export function times(...nums) {
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if (nums.length > 2) {
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return iteratorOperation(nums, times);
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}
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const [num1, num2] = nums;
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const num1Changed = float2Fixed(num1);
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const num2Changed = float2Fixed(num2);
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const baseNum = digitLength(num1) + digitLength(num2);
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const leftValue = num1Changed * num2Changed;
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checkBoundary(leftValue);
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return leftValue / Math.pow(10, baseNum);
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}
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/**
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* 高精度加法
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* @export
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*/
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export function plus(...nums) {
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if (nums.length > 2) {
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return iteratorOperation(nums, plus);
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}
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const [num1, num2] = nums;
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// 取最大的小数位
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const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
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// 把小数都转为整数然后再计算
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return (times(num1, baseNum) + times(num2, baseNum)) / baseNum;
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}
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/**
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* 高精度减法
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* @export
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*/
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export function minus(...nums) {
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if (nums.length > 2) {
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return iteratorOperation(nums, minus);
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}
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const [num1, num2] = nums;
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const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
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return (times(num1, baseNum) - times(num2, baseNum)) / baseNum;
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}
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/**
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* 高精度除法
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* @export
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*/
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export function divide(...nums) {
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if (nums.length > 2) {
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return iteratorOperation(nums, divide);
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}
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const [num1, num2] = nums;
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const num1Changed = float2Fixed(num1);
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const num2Changed = float2Fixed(num2);
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checkBoundary(num1Changed);
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checkBoundary(num2Changed);
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// 重要，这里必须用strip进行修正
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return times(
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num1Changed / num2Changed,
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strip(Math.pow(10, digitLength(num2) - digitLength(num1))),
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);
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}
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/**
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* 四舍五入
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* @export
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*/
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export function round(num, ratio) {
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const base = Math.pow(10, ratio);
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let result = divide(Math.round(Math.abs(times(num, base))), base);
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if (num < 0 && result !== 0) {
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result = times(result, -1);
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}
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// 位数不足则补0
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return result;
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}
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/**
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* 是否进行边界检查，默认开启
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* @param flag 标记开关，true 为开启，false 为关闭，默认为 true
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* @export
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*/
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export function enableBoundaryChecking(flag = true) {
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_boundaryCheckingState = flag;
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}
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export default {
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times,
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plus,
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minus,
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divide,
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round,
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enableBoundaryChecking,
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};
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