decode-named-character-reference/index.dom.js

Decode named character references

/// <reference lib="dom" />

/* eslint-env browser */

const element = document.createElement('i')

/**
 * @param {string} value
 * @returns {string | false}
 */
export function decodeNamedCharacterReference(value) {
  const characterReference = '&' + value + ';'
  element.innerHTML = characterReference
  const character = element.textContent

  // Some named character references do not require the closing semicolon
  // (`&not`, for instance), which leads to situations where parsing the assumed
  // named reference of `&notit;` will result in the string `¬it;`.
  // When we encounter a trailing semicolon after parsing, and the character
  // reference to decode was not a semicolon (`&semi;`), we can assume that the
  // matching was not complete.
  if (
    // @ts-expect-error: TypeScript is wrong that `textContent` on elements can
    // yield `null`.
    character.charCodeAt(character.length - 1) === 59 /* `;` */ &&
    value !== 'semi'
  ) {
    return false
  }

  // If the decoded string is equal to the input, the character reference was
  // not valid.
  // @ts-expect-error: TypeScript is wrong that `textContent` on elements can
  // yield `null`.
  return character === characterReference ? false : character
}