Build a calendar from scratch with react and tailwind css.

Calendar components are very popular and we can easily get a lib from npm. However calendar components can be also a hard one to style due to it comes with a set of builtin css. So we can build a calendar on our own to fit what we need and what we have set up.

Getting started.

The calendar I built in this post can be found here https://maxaledigheten.info/.

Install dependencies

It is actually not so difficult to build a calendar. First we need to install libraries for building this.

• tailwindcss for ui css.
• dayjs for working with datime.

Build a month calendar

In the application we render 12 months calendar. The core component here is a month calendar. The month calendar takes only two props month and year which is quite straightforward. The component will look like this

<MonthCalendar year={2022} month={4} key={4} />

We will start with week days to render

const today = dayjs().set('year', year);
const startWeek = today.startOf("isoWeek");
const weekDays = Array.from(new Array(7).keys()).map((index) => {
    return startWeek.add(index, "day");
  });

We get number of days in the month to render

const startOfMonth = today.set("month", month).startOf("month");
  const startOfFirstWeek = startOfMonth.startOf("isoWeek");
  const daysToFirstDay = startOfMonth.diff(startOfFirstWeek, "day");
  const daysToPrepend = Array.from(new Array(daysToFirstDay).keys());
  const daysInMonth = Array.from(new Array(startOfMonth.daysInMonth()).keys());

• daysToPrepend is the number of days in the first week of the month but from the previous month.

Last step is to gather data and then render

<div className="grid grid-cols-7 mt-2 rounded-md border overflow-hidden flex-1"> 
 {weekDays.map((weekDay, index) => (
          <div className="text-center" key={`weekday_${index}`}>
            {weekDay.format("ddd")}
          </div>
        ))}
{daysToPrepend.map((day) => (
          <div key={`prepend_${day}`}></div>
        ))}
{daysInMonth.map((day) => {
          const key = getDate(startOfMonth, day);
          return (
            <div
              className={`text-center `}
              key={key}
            >
              {day + 1}
            </div>
          )
        })}
</div>

• so we use a grid of 7 columns which corresponds to 7 days in a week.
• to render days in the right order we need to compensate with daysToPrepend.

TLDR

with the help of tailwind css and dayjs so to build a calendar component is quite simple and straightforward. Life is getting easier when we have the help from grid also.