Number.prototype.toLocaleString()

The toLocaleString() method of Number values returns a string with a language-sensitive representation of this number. In implementations with Intl.NumberFormat API support, this method delegates to Intl.NumberFormat.

Every time toLocaleString is called, it has to perform a search in a big database of localization strings, which is potentially inefficient. When the method is called many times with the same arguments, it is better to create an Intl.NumberFormat object and use its format() method, because a NumberFormat object remembers the arguments passed to it and may decide to cache a slice of the database, so future format calls can search for localization strings within a more constrained context.

Syntax example: toLocaleString()