Simple optimization of Jade attrs

JadeAttrsBench.js

self =
  {
  header: "Header",
  header2: "Header2",
  header3: "Header3",
  header4: "Header4",
  header5: "Header5",
  header6: "Header6",
  list: ['1', '2', '3', '4', '5', '6', '7', '8', '9', '10']
  };

attrs1 = function (obj, escaped) {
  var terse = obj.terse;

  delete obj.terse;
  var keys = Object.keys(obj)
    , len = keys.length;

  var s = ' ';
  if (len) {
    for (var i = 0; i < len; ++i) {
      var key = keys[i]
        , val = obj[key];

      if ('boolean' == typeof val || null == val) {
        if (val) {
          terse
            ? (s+= key + ' ')
            : (s+= key + '="' + key + '" ');
        }
      } else if (0 == key.indexOf('data') && 'string' != typeof val) {
        s += key + '="' + JSON.stringify(val) + '" ';
      } else if ('class' == key && Array.isArray(val)) {
        s += key + '="' + exports.escape(val.join(' ')) + '" ';
      } else if (escaped[key]) {
        s += key + '="' + exports.escape(val) + '" ';
      } else {
        s += key + '="' + val + '" ';
      }
    }
  }

  return s.substr(0, s.length-1);
};

attrs2 = function (obj, escaped) {
  var terse = obj.terse;

  delete obj.terse;
  var keys = Object.keys(obj)
    , len = keys.length;

  var s = '';
  if (len) {
    for (var i = 0; i < len; ++i) {
      var key = keys[i]
        , val = obj[key];

      if ('boolean' == typeof val || null == val) {
        if (val) {
          terse
            ? (s+= ' ' + key)
            : (s+= ' ' + key + '="' + key + '"');
        }
      } else if (0 == key.indexOf('data') && 'string' != typeof val) {
        s += ' ' + key + '="' + JSON.stringify(val) + '"';
      } else if ('class' == key && Array.isArray(val)) {
        s += ' ' + key + '="' + exports.escape(val.join(' ')) + '"';
      } else if (escaped[key]) {
        s += ' ' + key + '="' + exports.escape(val) + '"';
      } else {
        s += ' ' + key + '="' + val + '"';
      }
    }
  }

  return s;
};

jt1 = function ()
  {
  //var attrs = jade.attrs, escape = jade.escape, rethrow = jade.rethrow;
  var buf = [];
  //var self = locals || {};
  var interp;
  buf.push('<div><h1');
  buf.push(attrs1({ "class": ('header') }, {}));
  buf.push('>');
  var __val__ = self.header
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h1><h2');
  buf.push(attrs1({ "class": ('header2') }, {}));
  buf.push('>');
  var __val__ = self.header2
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h2><h3');
  buf.push(attrs1({ "class": ('header3') }, {}));
  buf.push('>');
  var __val__ = self.header3
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h3><h4');
  buf.push(attrs1({ "class": ('header4') }, {}));
  buf.push('>');
  var __val__ = self.header4
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h4><h5');
  buf.push(attrs1({ "class": ('header5') }, {}));
  buf.push('>');
  var __val__ = self.header5
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h5><h6');
  buf.push(attrs1({ "class": ('header6') }, {}));
  buf.push('>');
  var __val__ = self.header6
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h6><ul');
  buf.push(attrs1({ "class": ('list') }, {}));
  buf.push('>');
  // iterate self.list
  (function()
    {
    if ('number' == typeof self.list.length) 
      {
      for (var $index = 0, $$l = self.list.length; $index < $$l; $index++)
        {
        var item = self.list[$index];
        buf.push('<li');
        buf.push(attrs1({ "class": ('item') }, {}));
        buf.push('>');
        var __val__ = item
        buf.push(null == __val__ ? "" : __val__);
        buf.push('</li>');
        }
      }
    else 
      {
      for (var $index in self.list)
        {
        if (self.list.hasOwnProperty($index))
          {
          var item = self.list[$index];

          buf.push('<li');
          buf.push(attrs({ "class": ('item') }, {}));
          buf.push('>');
          var __val__ = item
          buf.push(null == __val__ ? "" : __val__);
          buf.push('</li>');
          }
        }
      }
  }).call(this);
  buf.push('</ul></div>');return new Buffer(buf.join(""));
  }

jt2 = function ()
  {
  //var attrs = jade.attrs, escape = jade.escape, rethrow = jade.rethrow;
  var buf = [];
  //var self = locals || {};
  var interp;
  buf.push('<div><h1');
  buf.push(attrs2({ "class": ('header') }, {}));
  buf.push('>');
  var __val__ = self.header
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h1><h2');
  buf.push(attrs2({ "class": ('header2') }, {}));
  buf.push('>');
  var __val__ = self.header2
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h2><h3');
  buf.push(attrs2({ "class": ('header3') }, {}));
  buf.push('>');
  var __val__ = self.header3
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h3><h4');
  buf.push(attrs2({ "class": ('header4') }, {}));
  buf.push('>');
  var __val__ = self.header4
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h4><h5');
  buf.push(attrs2({ "class": ('header5') }, {}));
  buf.push('>');
  var __val__ = self.header5
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h5><h6');
  buf.push(attrs2({ "class": ('header6') }, {}));
  buf.push('>');
  var __val__ = self.header6
  buf.push(null == __val__ ? "" : __val__);
  buf.push('</h6><ul');
  buf.push(attrs2({ "class": ('list') }, {}));
  buf.push('>');
  // iterate self.list
  (function()
    {
    if ('number' == typeof self.list.length) 
      {
      for (var $index = 0, $$l = self.list.length; $index < $$l; $index++)
        {
        var item = self.list[$index];
        buf.push('<li');
        buf.push(attrs2({ "class": ('item') }, {}));
        buf.push('>');
        var __val__ = item
        buf.push(null == __val__ ? "" : __val__);
        buf.push('</li>');
        }
      }
    else 
      {
      for (var $index in self.list)
        {
        if (self.list.hasOwnProperty($index))
          {
          var item = self.list[$index];

          buf.push('<li');
          buf.push(attrs({ "class": ('item') }, {}));
          buf.push('>');
          var __val__ = item
          buf.push(null == __val__ ? "" : __val__);
          buf.push('</li>');
          }
        }
      }
  }).call(this);
  buf.push('</ul></div>');return new Buffer(buf.join(""));
  }

var Benchmark = require('benchmark')
var suite = new Benchmark.Suite

suite
.add('jt1 - (attrs +,substr)', jt1)
.add('jt2 - (attrs +,prepend)  ', jt2)
.on('cycle', function (event, bench) {
  console.log(bench.toString());
})
.on('complete', function () {
  console.log('Fastest is ' + this.filter('fastest').pluck('name'))
})
.run();

SubstrPrependBench.js

var Benchmark = require('benchmark');

var suite = new Benchmark.Suite,
    input = 'blockquote hello\n  p World!\n';

suite
.add('substr', function () {
  var i = 3, s = ' ';
  while (i--) {
    s += input + '; ';
  }
  return s.substr(0, s.length - 1);
})
.add('prepend', function () {
  var i = 3, s = '';
  while (i--) {
    s += ' ' + input + ';';
  }
  return s;
})
.on('cycle', function (event, bench) {
  console.log(bench.toString());
})
.on('complete', function () {
  console.log('Fastest is ' + this.filter('fastest').pluck('name'));
})
.run();

JadeAttrsBench.js

jt1 - (attrs +,substr) x 35,110 ops/sec ±5.05% (51 runs sampled)
jt2 - (attrs +,prepend)   x 39,391 ops/sec ±4.12% (56 runs sampled)
Fastest is jt2 - (attrs +,prepend)

SubstrPrependBench.js

substr x 4,607,894 ops/sec ±3.05% (57 runs sampled)
prepend x 24,530,811 ops/sec ±2.70% (57 runs sampled)
Fastest is prepend

The SubstrPrependBench.js is a better direct measure of doing three concats per loop instead of two concats plus a substr at the end.

JadeAttrsBench.js shows it in action with the rest of the stuff.