foo.js

var suite = new (require("benchmark").Suite);

var stoper    = '<~_#@!';
var stoperRE  = /<~_#@!/g;

function format(msg, arg) {
  return msg + ":" + arg;
}

function varify_puzrin(phrase, params) {
  // quick-check for speed
  if (phrase.indexOf('#{') === -1) { return phrase; }

  // 1. Replace \#{ escaped case with sequence, that will never heppen.
  // That's a dirty hack, but it works & simplifies code.
  // 2. Replace #{variables} with values
  // 3. Return back escaped sequence & unescape it.

  return phrase
    .replace(/\\#{/g, stoper)
    .replace(/#{(.+?)}/g, function (__, name) {
      return (params[name] !== undefined) ?
        params[name] : format('[missed variable: %s]', name);
    })
    .replace(stoperRE, '#{');
}

function varify_puzrin_2(phrase, params) {
  // quick-check for speed
  if (phrase.indexOf('#{') === -1) { return phrase; }

  // 1. Replace \#{ escaped case with sequence, that will never heppen.
  // That's a dirty hack, but it works & simplifies code.
  // 2. Replace #{variables} with values
  // 3. Return back escaped sequence & unescape it.

  return phrase
    .replace(/\\#{/g, stoper)
    .replace(/#{([^}]+)}/g, function (__, name) {
      return (params[name] !== undefined) ?
        params[name] : format('[missed variable: %s]', name);
    })
    .replace(stoperRE, '#{');
}

function varify_ixti(phrase, params) {
  // quick-check for speed
  if (phrase.indexOf('#{') === -1) { return phrase; }

  return phrase.replace(/(\\?)#{(.+?)}/g, function (m, esc, name) {
    if (esc) { return m; }
    if (undefined !== params[name]) { return params[name]; }
      return format('[missed variable: %s]', name);
  });
}

function varify_ixti_2(phrase, params) {
  // quick-check for speed
  if (phrase.indexOf('#{') === -1) { return phrase; }

  return phrase.replace(/(\\?)#{([^}]+)}/g, function (m, esc, name) {
    if (esc) { return m; }
    if (undefined !== params[name]) { return params[name]; }
      return format('[missed variable: %s]', name);
  });
}

var str_1 = "foo #{foo} \\#{foo}";
var str_2 = "foo #{foo} \\#{foo} #{bar}";
var str_3 = "foo #{foo} \\#{foo} #{bar} \\#{bar}";

suite.add("varify_puzrin", function() {
  varify_puzrin(str_1, { foo: "bar", bar: "foo" });
  varify_puzrin(str_2, { foo: "bar", bar: "foo" });
  varify_puzrin(str_3, { foo: "bar", bar: "foo" });
});

suite.add("varify_puzrin_2", function() {
  varify_puzrin_2(str_1, { foo: "bar", bar: "foo" });
  varify_puzrin_2(str_2, { foo: "bar", bar: "foo" });
  varify_puzrin_2(str_3, { foo: "bar", bar: "foo" });
});

suite.add("varify_ixti", function () {
  varify_ixti(str_1, { foo: "bar", bar: "foo" });
  varify_ixti(str_2, { foo: "bar", bar: "foo" });
  varify_ixti(str_3, { foo: "bar", bar: "foo" });
});

suite.add("varify_ixti_2", function () {
  varify_ixti_2(str_1, { foo: "bar", bar: "foo" });
  varify_ixti_2(str_2, { foo: "bar", bar: "foo" });
  varify_ixti_2(str_3, { foo: "bar", bar: "foo" });
});

suite.on('cycle', function(event) {
  console.log(String(event.target));
});

suite.on('complete', function() {
  console.log('Fastest is ' + this.filter('fastest').pluck('name'));
});

suite.run();