How to loop through an array and continue at beginning once it reaches end?

June 30, 2022

My problem:

I have an array called "weekdays":

const weekdays = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];

Imagine it is Saturday and I want to know how many days it is until Tuesday (obviously 3 days). How can I loop through the array – starting at "Sat" and continue at the beginning until it reaches "Tue"?

My code so far:

const weekdays = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];

const start = weekdays.indexOf("Sat"); 
const end = weekdays.indexOf("Tue"); 
let howManyDays = 0;

for (let i = start; i < end; i = (i + 1) % weekdays.length) {
  howManyDays = howManyDays + 1;
}

However, it seems to be that "howManyDays" is still 0 when I run the code in the console in the browser.

>Solution :

This loop seems most appropriate to the question asked. Although a bit silly if you run 2 indexOf you already got the distance. just need to substract and module array length. But this approach is good for the loop, because you can just compare the values as you go until you find "Tue"

const weekdays = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];

const start = weekdays.indexOf("Sat");
const end = weekdays.indexOf("Tue");
let howManyDays = 0;

for (let i = start; i != end; i++) {
  i = i % weekdays.length;
  howManyDays = howManyDays + 1;
}

console.log(howManyDays)