为什么使用 MAX_SAFE_INTEGER 生成随机整数时数字分布不准确？

Question

尝试使用 MAX_SAFE_INTEGER 生成数字时，我注意到一些奇怪的事情，我确信这与数字在 javascript 中存储的方式有关，但我不明白它到底是什么。

Math.floor(Math.random() * Number.MAX_SAFE_INTEGER) // Always returns an odd number
Math.floor(Math.random() * (Number.MAX_SAFE_INTEGER - 1)) // Returns an odd number 75% of the time
Math.ceil(Math.random() * Number.MAX_SAFE_INTEGER) // Has a 50/50 chance to return odd or even

如何解释这种行为以及在 Math.floor 中可以使用的最大整数是多少来获得 50/50 比率？

class RandomNumberCounter {
    constructor() {
        this.evenCount = 0;
        this.oddCount = 0;
    }

    generateNumbersAndCount() {
        for (let i = 0; i < 10000; i++) {
            const randomNumber = Math.floor(Math.random() * Number.MAX_SAFE_INTEGER);
            if (randomNumber % 2 === 0) {
                this.evenCount++;
            } else {
                this.oddCount++;
            }
        }
    }

    printCounts() {
        console.log("Number of even numbers:", this.evenCount);
        console.log("Number of odd numbers:", this.oddCount);
    }
}

const randomNumberCounter = new RandomNumberCounter();
randomNumberCounter.generateNumbersAndCount();
randomNumberCounter.printCounts();

Answer 1

class RandomNumberCounter {
    constructor() {
        this.evenCount = 0;
        this.oddCount = 0;
    }

    generateNumbersAndCount() {
        for (let i = 0; i < 10000; i++) {
            // Changed
            const randomNumber = Math.floor(
              Number.MAX_SAFE_INTEGER * (3 * (Math.random() - 0.5))
            );
            if (randomNumber % 2 === 0) {
                this.evenCount++;
            } else {
                this.oddCount++;
            }
        }
    }

    printCounts() {
        console.log("Number of even numbers:", this.evenCount);
        console.log("Number of odd numbers:", this.oddCount);
    }
}

const randomNumberCounter = new RandomNumberCounter();
randomNumberCounter.generateNumbersAndCount();
randomNumberCounter.printCounts();