I have two "exact" functions and one doesn't work

May 11, 2022

I have two functions that are, from what I can tell, exactly the same. The only difference is one is a concise body and the other is the pre-ES6 long version. The concise version works and the other doesn’t. What’s the problem with the longer version?

//this version of the getActualSleepHours function works
const getActualSleepHours = () =>
  getSleepHours('monday') +
  getSleepHours('tuesday') +
  getSleepHours('wednesday') +
  getSleepHours('thursday') +
  getSleepHours('friday') +
  getSleepHours('saturday') +
  getSleepHours('sunday');

//this version of the getActualSleepHours function doesn't work
const getActualSleepHours = function() {
  getSleepHours('monday') +
    getSleepHours('tuesday') +
    getSleepHours('wednesday') +
    getSleepHours('thursday') +
    getSleepHours('friday') +
    getSleepHours('saturday') +
    getSleepHours('sunday');
}

>Solution :

The () => something() syntax inserts an implicit return before something(). To make these functions equivalent add a return to the function:

function() {
  return getSleepHours('monday') +
    getSleepHours('tuesday') +
    getSleepHours('wednesday') +
    getSleepHours('thursday') +
    getSleepHours('friday') +
    getSleepHours('saturday') +
    getSleepHours('sunday');
}