Node.JS 中基于概率的函数

Question

我想创建一个功能，当点击打开箱子时，这个人会得到一个随机角色，基于他们每个 class:

的概率

1 - 常见：90% 2 - 稀有：8% 3 - 超级稀有：2%

这在 Node.JS 中可行吗？

Answer 1

这确实是可能的，而且在任何语言中都是可能的，因为这只是生成一个随机数（参见 Math.Random()）并做一些数学运算！

下面是一个代码注释示例，用于解释正在发生的事情：

 // The actual function to draw a character class
function drawCharacterClass() {
  // We generate a random number between 0 and 1
  const r = Math.random();
  // If the number is between 0 and 0.02 (included) - so 2% chance
  if (r <= 0.02)
    return "Super Rare";
  // If the number is between 0.02 (not included) and 0.10 - so 8% chance.
  if (r <= 0.10)
    return "Rare";
  // If the number is anything else, so between 0.10 (not included) and 1 - so 90% chance.
  else
    return "Common";
}

// ===== ===== ===== Testing code below ===== ===== =====

// Now let's make a function that draw a lot of characters and record how many of each we got, this way we can make sure the drawCharacterClass() function is correct
function checkProbabilities(sample) {
  const res = {};
  for (let i = 0; i < sample; ++i) {
    const c = drawCharacterClass();
    res[c] = ++res[c] || 0;
  }
  return res;
}

// Let's poll 10 million characters.
// The higher the number the more precise it will be, but also slower.
const records = checkProbabilities(10000000);
// We count the total. We could also just use 10000000 directly.
const total = records["Common"] + records["Rare"] + records["Super Rare"];

// Now for each class of character, we count the amount we got from this class (records[class]) divided by the total of characters drawn. This will tell us what % of this class of character got drawn among the 10 millions draws.
console.log(`${Math.round(records["Common"] / total * 100)}% of Common.`); // Should say 90%
console.log(`${Math.round(records["Rare"] / total * 100)}% of Rare.`); // Should say 8%
console.log(`${Math.round(records["Super Rare"] / total * 100)}% of Super Rare.`); // Should say 2%

您可以执行这段代码，将使用代码段顶部的函数模拟绘制 1000 万个字符（可能需要几秒钟），然后计算每个字符的有效掉落率 class，让您确保它们是正确的。

请注意，这个功能drawCharacterClass()非常简单，只尊重你在问题中所说的内容。它的目标只是向您展示“是的，这是可能的”，但到目前为止 不是最好的方法 ，特别是如果您打算更改百分比、 classes，添加另一个 class，等等...

在这种情况下，您最好采用更 modular/generic 的方法，例如，您只需更改如下内容：

const classes = {
  "Common": 0.90,
  "Rare": 0.08,
  "Super Rare": 0.02
}

另请注意，它只会绘制某个 class 字符，而不是字符本身。
但是既然你知道如何从其他物品中随机选择一个物品（这里是几个 class 中的一个 class），那么从几个角色中选择一个角色应该不是很难！

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