I\'m trying to get this Javascript to do something if the day of the week matches any of the days listed in my statement, as well as restricting it to between 17:00 and 19:0
In this case, you better use a range check, because you need only two comparisons against of three or more - and it is better maintanable, just to change a value, if necessary.
if (dayOfWeek >= 4 && dayOfWeek <= 6 && hour >= 17 && hour < 19) {
The right OR conditions needs parenthesis, because of the precedence of &&
over ||
if ((dayOfWeek == 4 || dayOfWeek == 5 || dayOfWeek == 6) && hour >= 17 && hour < 19 ) {