/*jshint expr:true eqnull:true boss:true */

​

var compose = function() {

  return [].reduce.call(arguments, function(f,g) {

    return function() {

      return f(g.apply(this, arguments));

    };

  });

};

​

var join = function(f,g) {

  return function() {

    var as = arguments;

    return f.apply(this, as).concat(g.apply(this, as));

  };

};

​

var dot = function(prop) {

  return function(x) {

    return x[prop];

  };

};

​

var loop = function(prop) {

  return function(x) {

    var result = [];

    while (x = x[prop]) {

      result.push(x);

    }

    return result;

  };

};

​

var $ = (function(doc) {

  var toArray = function(x) {

    if (!x.length || typeof x != 'object') {

      return x; 

    }

    return Array.prototype.slice.call(x);

  };

  var flatten = function(xs) {

    return Array.prototype.concat.apply([], xs);

  };

  var unique = function(xs) {

    return xs.filter(function(x, idx) {

      return xs.indexOf(x) == idx;

    });

  };

  var query = function(sel, el) {

    return toArray((el||doc).querySelectorAll(sel));

  };

​

  function Dom(sel) {

    this.el = query(sel);

    this.first = this.el;

    this.length = this.el.length;

  }

  function $(sel) {

    return new Dom(sel); 

  }

  Dom.prototype = {

    _update: function(result) {

      this.prev = this.el;

      this.el = [].concat(result);

      this.length = this.el.length;

      return this;

    },

    get: function(idx) {

      return idx == null ? this.el : this.el[idx];

    },

    map: function(f) {

      var result = this.el.map(compose(toArray, f).bind(this));

      return this._update(unique(flatten(result)));

    },

    filter: function(sel) {

      var result = this.el.filter(function(x) {

        return query(sel, x.parentNode).indexOf(x) > -1;

      });

      return this._update(flatten(result));

    },

    end: function() {

      return this._update(this.first);

    },

    back: function() {

      return this._update(this.prev);

    },

    eq: function(idx) {

      return this._update(this.el[idx]);

    }

  };

  return $;

}(document));

​

// Example:

​

// Use these functions with `map` to chain

// Or you can also add them as methods

var children = dot('children');

var parents = loop('parentNode');

var prevAll = loop('previousElementSibling');

var nextAll = loop('nextElementSibling');

var siblings = join(prevAll, nextAll);

var text = dot('textContent');

​

var els = $('li').map(parents).get();

​

console.log(els);