@radicle/gray-matter/lib/excerpt.js

Parse front-matter from a string or file. Fast, reliable and easy to use. Parses YAML front matter by default, but also has support for YAML, JSON, TOML or Coffee Front-Matter, with options to set custom delimiters. Used by metalsmith, assemble, verb and

'use strict';

const defaults = require('./defaults');

module.exports = function(file, options) {
  const opts = defaults(options);

  if (file.data == null) {
    file.data = {};
  }

  if (typeof opts.excerpt === 'function') {
    return opts.excerpt(file, opts);
  }

  const sep = file.data.excerpt_separator || opts.excerpt_separator;
  if (sep == null && (opts.excerpt === false || opts.excerpt == null)) {
    return file;
  }

  const delimiter = typeof opts.excerpt === 'string'
    ? opts.excerpt
    : (sep || opts.delimiters[0]);

  // if enabled, get the excerpt defined after front-matter
  const idx = file.content.indexOf(delimiter);
  if (idx !== -1) {
    file.excerpt = file.content.slice(0, idx);
  }

  return file;
};