165 lines
4.7 KiB
JavaScript
165 lines
4.7 KiB
JavaScript
'use strict';
|
||
|
||
Object.defineProperty(exports, '__esModule', { value: true });
|
||
|
||
/**
|
||
* @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
|
||
*/
|
||
/**
|
||
* Correct the given number to specifying significant digits.
|
||
*
|
||
* @param num The input number
|
||
* @param precision An integer specifying the number of significant digits
|
||
*
|
||
* @example strip(0.09999999999999998) === 0.1 // true
|
||
*/
|
||
function strip(num, precision) {
|
||
if (precision === void 0) { precision = 15; }
|
||
return +parseFloat(Number(num).toPrecision(precision));
|
||
}
|
||
/**
|
||
* Return digits length of a number.
|
||
*
|
||
* @param num The 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;
|
||
}
|
||
/**
|
||
* Convert the given number to integer, support scientific notation.
|
||
* The number will be scale up if it is decimal.
|
||
*
|
||
* @param num The input number
|
||
*/
|
||
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);
|
||
}
|
||
/**
|
||
* Log a warning if the given number is out of bounds.
|
||
*
|
||
* @param num The input number
|
||
*/
|
||
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");
|
||
}
|
||
}
|
||
}
|
||
/**
|
||
* Create an operation to support rest params.
|
||
*
|
||
* @param operation The original operation
|
||
*/
|
||
function createOperation(operation) {
|
||
return function () {
|
||
var nums = [];
|
||
for (var _i = 0; _i < arguments.length; _i++) {
|
||
nums[_i] = arguments[_i];
|
||
}
|
||
var first = nums[0], others = nums.slice(1);
|
||
return others.reduce(function (prev, next) { return operation(prev, next); }, first);
|
||
};
|
||
}
|
||
/**
|
||
* Accurate multiplication.
|
||
*
|
||
* @param nums The numbers to multiply
|
||
*/
|
||
var times = createOperation(function (num1, num2) {
|
||
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);
|
||
});
|
||
/**
|
||
* Accurate addition.
|
||
*
|
||
* @param nums The numbers to add
|
||
*/
|
||
var plus = createOperation(function (num1, num2) {
|
||
// 取最大的小数位
|
||
var 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;
|
||
});
|
||
/**
|
||
* Accurate subtraction.
|
||
*
|
||
* @param nums The numbers to subtract
|
||
*/
|
||
var minus = createOperation(function (num1, num2) {
|
||
var baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
|
||
return (times(num1, baseNum) - times(num2, baseNum)) / baseNum;
|
||
});
|
||
/**
|
||
* Accurate division.
|
||
*
|
||
* @param nums The numbers to divide
|
||
*/
|
||
var divide = createOperation(function (num1, num2) {
|
||
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))));
|
||
});
|
||
/**
|
||
* Accurate rounding method.
|
||
*
|
||
* @param num The number to round
|
||
* @param decimal An integer specifying the decimal digits
|
||
*/
|
||
function round(num, decimal) {
|
||
var base = Math.pow(10, decimal);
|
||
var result = divide(Math.round(Math.abs(times(num, base))), base);
|
||
if (num < 0 && result !== 0) {
|
||
result = times(result, -1);
|
||
}
|
||
return result;
|
||
}
|
||
var _boundaryCheckingState = true;
|
||
/**
|
||
* Whether to check the bounds of number, default is enabled.
|
||
*
|
||
* @param flag The value to indicate whether is enabled
|
||
*/
|
||
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;
|