在JavaScript中使用科学记数法的陷阱

问题描述

这个问题不寻求开发者代码格式化意见。就个人而言，我更喜欢在我的JS代码中使用科学记数法，因为我相信它更具可读性。对我来说， 6e8 比 600000000 更具可读性。话虽这么说，我只是在寻找JS中用科学记数法指定数字的潜在风险和缺点。我不经常在野外看到它并且想知道是否有技术推理，或者仅仅是因为开发人员的druthers。

This question is not seeking developer code formatting opinions. Personally, I prefer to use scientific notation in my JS code when I can because I believe it is more readable. For me, 6e8 is more readable than 600000000. That being said, I am solely looking for potential risks and disadvantages specifying numbers in scientific notation in JS. I don't see it often in the wild and was wondering if there is technical reasoning for that or if it simply because of developer's druthers.

推荐答案

你没有看到科学记谱法经常在野外，因为在JS中实际输入的唯一数字往往是常量：

You don't see scientific notation "often in the wild" because the only numbers that actually get typed in JS tend to be constants:

• 以代码为中心的常量（例如枚举和级别）往往很小。


• 物理/数学常数（如π或e）倾向于非常具体。

这些都不会从科学记数法中获益太多。

Neither of these benefit from scientific notation too much.

我已经看到'在野外'as：

I have seen Plank's constant 'in the wild' as:

const h = 6.62607004e-34;
console.log('Plank', h);

其他通常有意义的地方是时间限制，例如一天中ms的数量为 864e5 。例如：

The other place it often makes sense is time limits, for instance the number of ms in a day as 864e5. For instance:

function addDaysToDate(date, days) {
  if (days === 0)
    return date;
  date.setTime(864e5 * days + date.valueOf());
  return date;
}

const now = new Date();
const thisTimeTomorrow = addDaysToDate(now, 1);
console.log('This time tomorrow', thisTimeTomorrow);

我认为没有任何技术理由不使用这种表示法，更多的是开发人员完全避免硬编码。

I don't think there's any technical reason not to use this notation, it's more that developers avoid hard coding numbers at all.

我认为没有任何风险。您可能必须小心字符串中的数字，但如果您这样做，则此语法比数字本地化（例如，输入的DE用户20.000,00的问题要小得多）。 ，期待 2e4 ，但得到 2e6 感谢不变数字格式交换千位和小数分隔符）。

I don't think there are any risks. You may have to be careful with numbers in strings, but if you're doing that then this syntax is a far smaller issue than, say, number localisation (for instance a DE user entering "20.000,00", expecting 2e4, but getting 2e6 thanks to invariant number formatting swapping the thousand and decimal separators).

我想补充一点，对于小数字，JS默认会输出该语法，但是避免大数到一点（由浏览器决定） ：

I'd add that JS will output that syntax by default anyway for small numbers, but avoids for large numbers up to a point (which varies by browser):

console.log('Very small', 1234 / 100000000000)
console.log('Large, but still full in some browsers', 1e17 * 1234)
console.log('Large, scientific', 1e35 * 1234)

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