Today I learned

Number.toLocaleString() can format a number according to the browser locale, or a specific locale.

18.95.toLocaleString("en")
// "18.95"

18.95.toLocaleString("fr")
// "18,95"

Integer literals need to be explicitly typed:

1000.toLocaleString()
// throws an error

Number(1000).toLocaleString('ch')
// returns "1’000"

Number(1000).toLocaleString('en')
// returns "1,000"

You don’t need the number constructor when using a variable:

let n = 1000
n.toLocaleString("en")
// "1,000"

It gets interesting when you add more options:

8.95.toLocaleString("en", {
  style: "currency",
  currency: "CHF"
})
// "CHF 8.95"

Number(2000).toLocaleString("en", {
 style: "currency",
 currency: "CHF"
})
// "CHF 2,000.00"

Number(2000).toLocaleString("en", {
 style: "currency",
 currency: "CHF",
 minimumFractionDigits: 0
})
// "CHF 2,000"