markdown-it/lib/rules_core/text_join.js

// Join raw text tokens with the rest of the text
//
// This is set as a separate rule to provide an opportunity for plugins
// to run text replacements after text join, but before escape join.
//
// For example, `\:)` shouldn't be replaced with an emoji.
//
'use strict';


module.exports = function text_join(state) {
  var j, l, tokens, curr, max, last,
      blockTokens = state.tokens;

  for (j = 0, l = blockTokens.length; j < l; j++) {
    if (blockTokens[j].type !== 'inline') continue;

    tokens = blockTokens[j].children;
    max = tokens.length;

    for (curr = 0; curr < max; curr++) {
      if (tokens[curr].type === 'text_special') {
        tokens[curr].type = 'text';
      }
    }

    for (curr = last = 0; curr < max; curr++) {
      if (tokens[curr].type === 'text' &&
          curr + 1 < max &&
          tokens[curr + 1].type === 'text') {

        // collapse two adjacent text nodes
        tokens[curr + 1].content = tokens[curr].content + tokens[curr + 1].content;
      } else {
        if (curr !== last) { tokens[last] = tokens[curr]; }

        last++;
      }
    }

    if (curr !== last) {
      tokens.length = last;
    }
  }
};