How to compare time in javascript?

use Date objects. Date.setHours() allows you to specify hour, minutes, seconds

var currentD = new Date();
var startHappyHourD = new Date();
startHappyHourD.setHours(17,30,0); // 5.30 pm
var endHappyHourD = new Date();
endHappyHourD.setHours(18,30,0); // 6.30 pm

console.log("happy hour?")
if(currentD >= startHappyHourD && currentD < endHappyHourD ){
    console.log("yes!");
}else{
    console.log("no, sorry! between 5.30pm and 6.30pm");
}