Formats a number according to a locale.

By default the locale is US english:

new Number(21.2).toLocaleString() //21.2

We can pass the locale as the first parameter:

new Number(21.2).toLocaleString('it') //21,2

This is eastern arabic

new Number(21.2).toLocaleString('ar-EG') //٢١٫٢

There are a number of options you can add, and I suggest to look at the MDN page to know more.