v135 · javascript

URL route matcher

Path templates like /users/:id/posts/:slug are ubiquitous in routing libraries. Building them safely requires escaping the literal segments with RegExp.escape() so a path like /api/v1.0/users doesn't turn into a regex bomb where . matches anything.

RegExp.escape: checking…
Route templates
Test URLs
Match results params extracted from matched segment
URL Matched route Params
Generated regexes RegExp.escape() applied to literal segments
TemplateCompiled regex
 
// Building a path matcher with RegExp.escape
function compileRoute(template) {
  // Split on :param tokens
  const parts = template.split(/(:[\w]+)/g);
  const paramNames = [];

  const pattern = parts.map(part => {
    if (part.startsWith(':')) {
      paramNames.push(part.slice(1));
      return '([^/]+)';          // capture group for the param
    }
    return RegExp.escape(part);  // literal segment — dots, slashes, etc. are safe
  }).join('');

  return { re: new RegExp('^' + pattern + '$'), paramNames };
}

// Without RegExp.escape, /api/v1.0/users matches /api/v1X0/users too
// because '.' is unescaped. With it, only the literal dot matches.

see also

references