JS implementation code to control the number of decimal places_javascript skills

//Decimal number control, can be rounded
function Fractional(n) {
//The number of decimal places to retain
var bit = 2;
//After adding the decimal point To extend 1 digit
bit;
//Convert number to string
n = n.toString();
//Get the decimal point position
var point = n.indexOf('. ');
//The length of n is greater than the length of reserved digits
if (n.length > point bit) {
//Whether the reserved decimal digit is greater than 4, greater than 4 carry
if (parseInt(n.substring(point bit, point bit 1)) > 4) {
return n.substring(0, point) "." (parseInt(n.substring(point 1, point bit)) 1);
}
else {
return n.substring(0, point) n.substring(point, point bit);
}
}
return n;
}