Function format 

pub fn format(value: f64, format: &str) -> String

Format value using a numeral.js format string (default "0,0" when empty).

NaN is treated as numeral’s null and formats as zero.

assert_eq!(format(1234.5678, "0,0.00"), "1,234.57");
assert_eq!(format(f64::NAN, "0,0"), "0");