js加减乘除--科学计数法-解决精度丢失
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 | '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 */ /** * 把错误的数据转正 * strip(0.09999999999999998)=0.1 */ function strip(num, precision) { if (precision === void 0) { precision = 12; } return +parseFloat(num.toPrecision(precision)); } /** * Return digits length of a number * @param {*number} num 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; } /** * 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) { if (num.toString().indexOf( 'e' ) === -1) { return Number(num.toString().replace( '.' , '' )); } var dLen = digitLength(num); return dLen > 0 ? strip(num * Math.pow(10, dLen)) : 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) { 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, num2) { var others = []; for ( var _i = 2; _i < arguments.length; _i++) { others[_i - 2] = arguments[_i]; } if (others.length > 0) { return times.apply(void 0, [times(num1, num2), others[0]].concat(others.slice(1))); } 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); } /** * 精确加法 */ function plus(num1, num2) { var others = []; for ( var _i = 2; _i < arguments.length; _i++) { others[_i - 2] = arguments[_i]; } if (others.length > 0) { return plus.apply(void 0, [plus(num1, num2), others[0]].concat(others.slice(1))); } var 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, num2) { var others = []; for ( var _i = 2; _i < arguments.length; _i++) { others[_i - 2] = arguments[_i]; } if (others.length > 0) { return minus.apply(void 0, [minus(num1, num2), others[0]].concat(others.slice(1))); } var 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, num2) { var others = []; for ( var _i = 2; _i < arguments.length; _i++) { others[_i - 2] = arguments[_i]; } if (others.length > 0) { return divide.apply(void 0, [divide(num1, num2), others[0]].concat(others.slice(1))); } 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)))); } /** * 四舍五入 */ function round(num, ratio) { var base = Math.pow(10, ratio); return divide(Math.round(times(num, base)), base); } var _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 */ function enableBoundaryChecking(flag) { if (flag === void 0) { flag = true ; } _boundaryCheckingState = flag; } //定义一个加法函数(小数相加) function floatCalc(arg1, arg2) { var r1, r2, m, n; try { r1 = arg1.toString().split( "." )[1].length; } catch (e) { r1 = 0; } try { r2 = arg2.toString().split( "." )[1].length; } catch (e) { r2 = 0; } m = Math.pow(10, Math.max(r1, r2)); //last modify by deeka //动态控制精度长度 n = (r1 >= r2) ? r1 : r2; return ((arg1 * m - arg2 * m) / m).toFixed(n); } var index = { strip: strip, plus: plus, minus: minus, times: times, divide: divide, round: round, digitLength: digitLength, float2Fixed: float2Fixed, enableBoundaryChecking: enableBoundaryChecking, floatCalc: floatCalc }; 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.floatCalc = floatCalc; exports[ 'default' ] = index; |
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