javascript - What does the following snippet do with num? -

i read other's code, there piece of code below. wondering method num?

 formatnumber: function (num, digit) {             var pow = math.pow(10, digit || 5);             return math.round(num * pow) / pow;     } 

btw when running formatnum(11.267898, 5), gave me 11.2679, ok?

essentially, function returns number precision. precision digit, 5 if not provided.

the return part brings many values (equal digit) decimal right left , discard rest , divides again original value reduces precision of digit.

regarding btw edit -

the value obtained correct. see details below

when call formatnum(11.267898, 5), you're asking number round 5 digit precision , number has 6 digit precision - precision digits after dot.

now when call num * pow number becomes 1126789.8 , when round number, rounds closest integer 11.26790. when divide pow (100000), number becomes 11.2679, discarding last 0 trailing 0 in precision pointless.