app/lib/text-fragment.mjs

Functions

Imports

It imports no other module of this repo. Imported by app/enhance/blog.ts.

Source

1// The directive matches the first occurrence, so a short phrase can land on the wrong paragraph.
2export const FRAGMENT_MIN_CHARS = 12;
3
4export const FRAGMENT_MAX_CHARS = 200;
5
6export const FRAGMENT_EDGE_WORDS = 6;
7
8/**
9 * `encodeURIComponent` leaves the hyphen, which the directive reserves: an unescaped one turns the
10 * rest of the passage into a suffix match.
11 *
12 * @param {string} text
13 */
14const encodePart = (text) => encodeURIComponent(text).replace(/-/g, "%2D");
15
16/**
17 * @param {string} selected raw selected text, as `Selection.toString()` yields it
18 * @returns {string | null} the value for `#:~:text=`, or null when the selection is too short
19 */
20export function textFragment(selected) {
21  const text = selected.trim().replace(/[^\S\n]+/g, " ");
22  if (text.length < FRAGMENT_MIN_CHARS) return null;
23
24  const words = text.split(/\s+/);
25  const edge = Math.min(FRAGMENT_EDGE_WORDS, words.length >> 1);
26
27  /*
28   * A selection crossing a block boundary (a newline from `Selection`) never matches as one exact
29   * string, and long passages are fragile against whitespace differences, so both use the range form.
30   */
31  if (edge > 0 && (text.length > FRAGMENT_MAX_CHARS || text.includes("\n"))) {
32    return `${encodePart(words.slice(0, edge).join(" "))},${encodePart(words.slice(-edge).join(" "))}`;
33  }
34  return encodePart(text);
35}