67 lines
1.9 KiB
JavaScript
67 lines
1.9 KiB
JavaScript
"use strict";
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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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function digitLength(num) {
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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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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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function checkBoundary(num) {
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{
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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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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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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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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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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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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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return result;
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}
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exports.round = round;
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