Intl.NumberFormat

new Intl.NumberFormat('cs-CZ', {
   style: 'currency', 
   currency: 'CZK' 
}).format(123456.7891)
// '123 456,79 Kč'

new Intl.NumberFormat('cs-CZ', { 
    minimumFractionDigits: 1 
}).format(123456.7891)
// '123 456,789'

new Intl.NumberFormat('cs-CZ', {
   maximumFractionDigits: 1
}).format(123456.7891)
// '123 456,8'

new Intl.NumberFormat('cs-CZ', {
   maximumSignificantDigits: 2
}).format(123456.7891)
// '120 000'

new Intl.NumberFormat('cs-CZ', {
   maximumSignificantDigits: 2
}).formatRange(num, num)
// '~120 000'

new Intl.NumberFormat('cs-CZ', {
   currency: "CZK"
}).formatToParts(123456.7891)
/* '[
   {"type":"integer","value":"123"},
   {"type":"group","value":" "},
   {"type":"integer","value":"456"},
   {"type":"decimal","value":","},
   {"type":"fraction","value":"789"}
]'
*/