hast-util-reading-time

hast utility to estimate the reading time, taking readability of the document into account.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • readingTime(tree, options?)
• Types
• Compatibility
• Security
• Related
• Contribute
• License

What is this?

This package is a utility that takes a hast (HTML) syntax tree and estimates the reading time, taking readability of the document and a target age group into account.

The algorithm works as follows:

• estimate the WPM (words per minute) of the audience age based on the facts that English can be read at ±228 WPM (Trauzettel-Klosinski), and that reading rate increases 14 WPM per grade (Carver)
• apply the readability algorithms Dale—Chall, Automated Readability, Coleman-Liau, Flesch, Gunning-Fog, SMOG, and Spache
• adjust the WPM of the audience for whether the readability algorithms estimate its above or below their level
• wordCount / adjustedWpm = readingTime

⚠️ Important: this algorithm is specific to English.

When should I use this?

This is a small utility useful when you have an AST, know your audience, and want a really smart reading time algorithm.

The rehype plugin rehype-infer-reading-time-meta wraps this utility to figure, for use with rehype-meta.

Install

This package is ESM only. In Node.js (version 12.20+, 14.14+, or 16.0+), install with npm:

npm install hast-util-reading-time

In Deno with esm.sh:

import {readingTime} from "https://esm.sh/hast-util-reading-time@1"

In browsers with esm.sh:

<script type="module">
  import {readingTime} from "https://esm.sh/hast-util-reading-time@1?bundle"
</script>

Use

Say our document example.html contains (from “Word per minute: Alphanumeric entry” on Wikipedia:

<p>Since the length or duration of words is clearly variable, for the purpose of measurement of text entry, the definition of each "word" is often standardized to be five characters or keystrokes long in English, including spaces and punctuation. For example, under such a method applied to plain English text the phrase "I run" counts as one word, but "rhinoceros" and "let's talk" would both count as two.</p>
<p>Karat et al. found that one study of average computer users in 1999, the average rate for transcription was 32.5 words per minute, and 19.0 words per minute for composition. In the same study, when the group was divided into "fast", "moderate", and "slow" groups, the average speeds were 40 wpm, 35 wpm, and 23 wpm, respectively.</p>
<p>With the onset of the era of desktop computers, fast typing skills became much more widespread.</p>
<p>An average professional typist types usually in speeds of 43 to 80 wpm, while some positions can require 80 to 95 (usually the minimum required for dispatch positions and other time-sensitive typing jobs), and some advanced typists work at speeds above 120 wpm. Two-finger typists, sometimes also referred to as "hunt and peck" typists, commonly reach sustained speeds of about 37 wpm for memorized text and 27 wpm when copying text, but in bursts may be able to reach much higher speeds. From the 1920s through the 1970s, typing speed (along with shorthand speed) was an important secretarial qualification and typing contests were popular and often publicized by typewriter companies as promotional tools.</p>

…and our module example.js looks as follows:

import fs from 'node:fs/promises'
import {fromHtml} from 'hast-util-from-html'
import {readingTime} from 'hast-util-reading-time'

const tree = fromHtml(await fs.readFile('example.html'), {fragment: true})

console.log(
  `It takes about ${Math.ceil(readingTime(tree, {age: 18}))}-${Math.ceil(readingTime(tree, {age: 14}))}m to read`
)

…now running node example.js yields:

It takes about 2-3m to read

API

This package exports the identifier readingTime. There is no default export.

readingTime(tree, options?)

Estimate the reading time.

options

Configuration (optional).

options.age

Target age group (number, default: 16). This is the age your target audience was still in school. Set it to 18 if you expect all readers to have finished high school, 21 if you expect your readers to all be college graduates, etc.

Returns

Reading time in minutes (number). The result is not rounded so it’s possible to retrieve estimated seconds from it.

Types

This package is fully typed with TypeScript. It exports the additional type Options.

Compatibility

Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, 16.0+, and 18.0+. Our projects sometimes work with older versions, but this is not guaranteed.

Security

Use of hast-util-reading-time is safe.

Related

• rehype-infer-reading-time-meta — infer reading time as file metadata from the document
• rehype-meta — add metadata to the head of a document

Contribute

See contributing.md in syntax-tree/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

License

MIT © Titus Wormer