1const formatToCurrency = amount => {
2  return "$" + amount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, "$&,");
3};
4formatToCurrency(12.34546); //"$12.35"
5formatToCurrency(42345255.356); //"$42,345,255.36

1function formatToCurrency(amount){
2    return (amount).toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,'); 
3}
4formatToCurrency(12.34546); //"12.35"
5formatToCurrency(42345255.356); //"42,345,255.36"

1(12345.67).toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');  // 12,345.67

1const formatter = new Intl.NumberFormat('en-US', {
2  style: 'currency',
3  currency: 'USD',
4  minimumFractionDigits: 2
5})
6
7formatter.format(1000) // "$1,000.00"
8formatter.format(10) // "$10.00"
9formatter.format(123233000) // "$123,233,000.00"

1// Create our number formatter.
2var formatter = new Intl.NumberFormat('en-US', {
3  style: 'currency',
4  currency: 'USD',
5});
6
7formatter.format(2500); /* $2,500.00 */

1// Javascript has a number formatter (part of the Internationalization API).
2
3const number = 123456.789;
4
5// another example 
6console.log(new Intl.NumberFormat('ja-JP',  {
7  style: 'currency',
8  currency: 'BWP',
9}).format(number));
10
11// MORE INFO ->  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat
12
13