prototype.js 1.4 原代码阅读

        switch (attribute.operator) {
          case '=':       conditions.push(value + ' == ' + attribute.value.inspect()); break;
          case '~=':      conditions.push(splitValueBy(' ') + '.include(' + attribute.value.inspect() + ')'); break;
          case '|=':      conditions.push(
                            splitValueBy('-') + '.first().toUpperCase() == ' + attribute.value.toUpperCase().inspect()
                          ); break;
          case '!=':      conditions.push(value + ' != ' + attribute.value.inspect()); break;
          case '':
          case undefined: conditions.push(value + ' != null'); break;
          default:        throw 'Unknown operator ' + attribute.operator + ' in selector';
        }
      });
    }

    return conditions.join(' && ');
  },

  compileMatcher: function() {
    this.match = new Function('element', 'if (!element.tagName) return false; \
      return ' + this.buildMatchExpression());
  },

  findElements: function(scope) {
    var element;

    if (element = $(this.params.id))
      if (this.match(element))
        if (!scope || Element.childOf(element, scope))
          return [element];

    scope = (scope || document).getElementsByTagName(this.params.tagName || '*');

    var results = [];
    for (var i = 0; i < scope.length; i++)
      if (this.match(element = scope[i]))
        results.push(Element.extend(element));

    return results;
  },

  toString: function() {
    return this.expression;
  }
}

function $$() {
  return $A(arguments).map(function(expression) {
    return expression.strip().split(/\s+/).inject([null], function(results, expr) {