support/compile.js
function parseConditionals(js) {
  var lines = js.split('\n')
    , len = lines.length
    , buffer = true
    , browser = false
    , buf = []
    , line
    , cond;

  for (var i = 0; i < len; ++i) {
    line = lines[i];
    if (/^ *\/\/ *if *(node|browser)/gm.exec(line)) {
      cond = RegExp.$1;
      buffer = browser = 'browser' == cond;
    } else if (/^ *\/\/ *end/.test(line)) {
      buffer = true;
      browser = false;
    } else if (browser) {
      buf.push(line.replace(/^( *)\/\//, '$1'));
    } else if (buffer) {
      buf.push(line);
    }
  }

  return buf.join('\n');
}
function parseConditionals(js) {
  var lines = js.split('\n')
    , len = lines.length
    , buffer = true
    , browser = false
    , buf = []
    , line
    , cond;

  for (var i = 0; i < len; ++i) {
    line = lines[i];
    if (/^ *\/\/ *if *(node|browser)/gm.exec(line)) {
      cond = RegExp.$1;
      buffer = browser = 'browser' == cond;
    } else if (/^ *\/\/ *end/.test(line)) {
      buffer = true;
      browser = false;
    } else if (browser) {
      buf.push(line.replace(/^( *)\/\//, '$1'));
    } else if (buffer) {
      buf.push(line);
    }
  }

  return buf.join('\n');
}
Parse the given `js`, currently supporting:

'if' ['node' | 'browser']
'end'