This markdown-it plugin replaces the "replacements" feature in markdown-it typographer, allowing you to customize the replacement rules (regular expression substitutions) done to inline text outside of autolinks.

There are four built-in replacement rules (mimicking some of the built-in markdown-it typographer):

• +- → ± (rule "plusminus")
• ... → … (rule "ellipsis")
• --- → — (rule "mdash")
• -- → – (rule "ndash")

Each rule can be turned off by specifying an option object when using the module (mapping each undesired rule name to false). Additional rules can be added by modifying the replacements module attribute (an array of rules, where each rule has a name rule.name, regular expression rule.re, substitution rule.sub, and boolean default on/off rule.default).

// Without smart quotes
md = require('markdown-it')()
.use(require('markdown-it-replacements'));
md.renderInline('Hello... "world"---');
          // -> 'Hello… "world"—'

// With smart quotes
md = require('markdown-it')({typographer: true})
.use(require('markdown-it-replacements'));
md.renderInline('Hello... "world"---');
          // -> 'Hello… “world”—'

// Using options to turn specific replacements on/off
md = require('markdown-it')({typographer: true})
.use(require('markdown-it-replacements'), {mdash: false});
md.renderInline('Hello... "world"---');
          // -> 'Hello… “world”---'

// Adding custom replacements
mir = require('markdown-it-replacements');
mir.replacements.push({
  name: 'allcaps',
  re: /[a-z]/g,
  sub: function (s) { return s.toUpperCase(); },
  default: true
});
md = require('markdown-it')({typographer: true}).use(mir);
md.renderInline('Hello... "world"---');
          // -> 'HELLO… “WORLD”—'

• Unlike the built-in replacements rule, this module does not require the global typographer option to be set to true. (The reasoning being that, if you're using this module, you probably want to do the substitutions.) This means that the typographer option effectively controls whether to do smart-quote substitution.