Function diffHighlight

src/render-utils.ts:239–304

(
  diffLine1: string,
  diffLine2: string,
  isCombined: boolean,
  config: RenderConfig = {},
)

 * Highlight differences between @diffLine1 and @diffLine2 using <ins> and <del> tags
 */
export function diffHighlight(
  diffLine1: string,
  diffLine2: string,
  isCombined: boolean,
  config: RenderConfig = {},
): HighlightedLines {
  const { matching, maxLineLengthHighlight, matchWordsThreshold, diffStyle } = { ...defaultRenderConfig, ...config };

  const line1 = deconstructLine(diffLine1, isCombined, false);
  const line2 = deconstructLine(diffLine2, isCombined, false);

  if (line1.content.length > maxLineLengthHighlight || line2.content.length > maxLineLengthHighlight) {
    return {
      oldLine: {
        prefix: line1.prefix,
        content: escapeForHtml(line1.content),
      },
      newLine: {
        prefix: line2.prefix,
        content: escapeForHtml(line2.content),
      },
    };
  }

  const diff =
    diffStyle === 'char'
      ? jsDiff.diffChars(line1.content, line2.content)
      : jsDiff.diffWordsWithSpace(line1.content, line2.content);

  const changedWords: jsDiff.Change[] = [];
  if (diffStyle === 'word' && matching === 'words') {
    const removed = diff.filter(element => element.removed);
    const added = diff.filter(element => element.added);
    const chunks = matcher(added, removed);
    chunks.forEach(chunk => {
      if (chunk[0].length === 1 && chunk[1].length === 1) {
        const dist = distance(chunk[0][0], chunk[1][0]);
        if (dist < matchWordsThreshold) {
          changedWords.push(chunk[0][0]);
          changedWords.push(chunk[1][0]);
        }
      }
    });
  }

  const highlightedLine = diff.reduce((highlightedLine, part) => {
    const elemType = part.added ? 'ins' : part.removed ? 'del' : null;
    const addClass = changedWords.indexOf(part) > -1 ? ' class="d2h-change"' : '';
    const escapedValue = escapeForHtml(part.value);

    return elemType !== null
      ? `${highlightedLine}<${elemType}${addClass}>${escapedValue}</${elemType}>`
      : `${highlightedLine}${escapedValue}`;
  }, '');

  return {
    oldLine: {
      prefix: line1.prefix,