Convert minutes portion of time to decimal
Use const instead of let to declare variables if the value doesn't change.

You are executing time.split(':') twice.

A short method to convert a string to a number is the unary +.

JavaScript has the toFixed() method to format a number to a fixed number of digits:



function minuteConverter(time) {
   const [h, m] = time.split(':');
   const value = +h + +m / 60;
   return value.toFixed(2);
}