No, I’m not going to start a video channel on this topic. But I want to show you some things about numbers, you might not have known before. The answer, however, as we all know, is 42.

Types of numbers

Let start with the very basics. You probably all know that in JavaScript, just like in many other programming languages, there are decimal number and floating-point numbers. But internally, they are all of the type Number. They are 64-bit, which should usually be enough for most code. But if you need really large numbers, you can also use BigInt to store them.

Some lesser known number types

Now that we know, that all (small) numbers are of type Number, we only know parts of the truth. We can have more than just two types. Here are the two typical ones, and some more, you might not have heard of or used in JavaScript:

42 // decimal
42.0 // float
042 // octal => 34 decimal - as digits after leading zero(s) are <= 8
099 // not octal, decimal 99, as digits after leading zero(s) are > 8
0o42 // explicit octal number - either lower- or uppercase latin "o"
0x42 // hexadecimal => 66 decimal - either lower- or uppercase latin "x"
0b101010 // binary 42, nice sequence ;) - either lower- or uppercase lat. "b"
0.042e3 // exponential number 42 - either lower- or uppercase latin "e"
42n // BigInt 42 - decimal followed by latin lower- "n" even for small number

Comparing numbers

As we have discussed earlier, except for BigInt, all numbers are the same type. Therefore, comparing the following numbers, these are the results:

42 === 42.0 // true
042 === 42 // false
0o42 === 34 // true
042 === 34 // true
099 === 99 // true
0x42 === 66 // true
42 === 0b101010 // true
42 === 0.042e3 // true
42n === 42 // false
42n == 42 // true

That last one might be (a bit) unexpected. So when comparing a BigInt to any other number, you cannot use the “strict equality operator”, since the numbers are of a different type.

If you want to find out, if a number is an integer, you can use a function from the Number object:

Number.isInteger(42) // true
Number.isInteger(42.001) // false
Number.isInteger(42.0) // true
Number.isInteger(42.000000000000001) // true

As you can see, this function will return true, if the number is an integer, or a floating-point number with a zero fraction – or a really small fraction. Unfortunately, there are no similar functions to check for other number types.

Now some fun part

Do you need some very long numbers in your code? Then you probably end up with something really hard to read. But there is a neat little trick to make them more readable:

// That's a huge number!
let rubiksCubeConfigurations = 43252003274489856000;
// As a string, it's easier to read, but this is bad code!
let sameNumberAsString = parseInt("43252003274489856000");
// How about this?
let easierToRead = 43_252_003_274_489_856_000;

That’s more readable, right? The funny thing is, that you can use an underscore at any place, just not at the beginning or end of the number, not after a leading zero, and not two underscores in a row. But many of us will probably use them like shown above.

Bonus: Formatting numbers

Now that we have seen how to make numbers more readable in code, here is a tip to make them easier to read for people from different countries. In the US, you would write a number like this: “123,456.789”. But in Germany, you would write “123.456,789”. If we look at the Number object again, we will find the toLocaleString() function, and this is how you can use it:

const number = 1234567.89;
// German
console.log(number.toLocaleString("de")); // 1,234,567.89
// English (United States)
console.log(number.toLocaleString("en-US")); // 1,234,567.89
// Englisch (India)
console.log(number.toLocaleString("en-IN")); // 12,34,567.89
// Ukrainian
console.log(number.toLocaleString("uk")); // 1 234 567,89
// Dzongkha
console.log(number.toLocaleString("dz")); // ༡༢,༣༤,༥༦༧.༨༩

Would you have known, how numbers are formatted in different languages? And in some languages, JavaScript will even output them with non latin letters. The same function can also be used to format currencies:

const costs = 123.4567;
// German with EUR
console.log(
    costs.toLocaleString("de-DE", { style: "currency", currency: "EUR" }),
); // 123,46 €

Conclusion

There are many really useful trick then dealing with numbers in JavaScript. I hope there was something for you, that will help you in a future project. I can also recommend to look at documentation of the other functions and features of the Number object.