Calculate reading time in Javascript

When starting this blog, I was inspired by other websites and realized that they all display the time it takes to read a post.

But how is it done? Here’s the snippet. 😉

function readingTime(post) {
  const WORDS_PER_MINUTE = 200;
  const regex = /\w+/g;
  const wordCount = post.match(regex)?.length || 0;

  return Math.ceil(wordCount / WORDS_PER_MINUTE);
}

How does it work?

We create a readingTime function, with a post parameter that would be the text we want to determine the reading time for.

function readingTime(post) {}

People read approximately between 200 and 250 words per minute, so we set a reference variable.

const WORDS_PER_MINUTE = 200;

The trick to finding the words is to use Regex.

const regex = /\w+/g;

Using the match method, we identify how many words match the regex. Finally, we add the || operator followed by a 0 in case no matches are found.

const wordCount = post.match(regex)?.length || 0;

We calculate the reading time by dividing the words found by the words per minute.

wordCount / WORDS_PER_MINUTE;

Then, using Math.ceil(), we get the approximate value:

function readingTime(post) {
  const WORDS_PER_MINUTE = 200;
  const regex = /\w+/g;
  const wordCount = post.match(regex)?.length || 0;

  return Math.ceil(wordCount / WORDS_PER_MINUTE);
}

const result = readingTime('Mi tiempo de lectura es de 1 min aprox.');

console.log(result); // resultado: 1

If you want a more approximate value, you can replace Math.ceil with Math.floor, Math.round, or Math.trunc depending on your needs.