js 计算精度问题

function add(num1, num2) {
    const factor = Math.pow(10, Math.max(decimalPlaces(num1), decimalPlaces(num2)));
    return (Math.round(num1 * factor) + Math.round(num2 * factor)) / factor;
}

function decimalPlaces(num) {
    const match = ('' + num).match(/(?:\.(\d+))?(?:[eE]([+-]?\d+))?$/);
    if (!match) { return 0; }
    return Math.max(0, (match[1] ? match[1].length : 0) - (match[2] ? +match[2] : 0));
}

console.log(add(0.1, 0.2)); // 输出 0.3

const Decimal = require('decimal.js');

const num1 = new Decimal(0.1);
const num2 = new Decimal(0.2);
const result = num1.plus(num2);

console.log(result.toString()); // 输出 0.3

const num1 = BigInt(9007199254740991);
const num2 = BigInt(1);
const result = num1 + num2;

console.log(result.toString()); // 输出 9007199254740992