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
|
* @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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|
/**
|
* 检测数字是否越界，如果越界给出提示
|
* @private
|
* @param {*number} num 输入数
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*/
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function checkBoundary(num) {
|
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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}
|
}
|
}
|
|
/**
|
* 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,
|
};
|
