Automatize querySelectorAll manipulation.

Collection.js

var t = console.log;


var select = function( selector ){
  return new Collection( document.querySelectorAll( selector ) );
};

var Collection = function( collection ){ 
  collection = collection || []; 
  this.collection = Array.prototype.slice.call(collection);
  this.length = this.collection.length;
};

Collection.prototype = {
  fn : function(){
    var params = Array.prototype.slice.call(arguments);
    var method = params.shift();
    for(var i=0; elt = this.collection[i] ; i++ ){
      elt[method].apply(elt,params);
    }
    return this;
  },
  each: function( handler ){
    for( var i=0,elt; elt = this.collection[i];i++ ){
      handler.call(elt,i);
    }
  },
  nth: function( n ){
    if( parseInt(n) == n ){
      return this.collection[n];
    }else{
      var multi=1, add = 0;
      if( n === 'even' ){
        multi = 2;
      }else if( n === 'odd' ){
        multi = 0;
      }else{
        var res = /([0-9]+)n/.exec(n);
        if(res) multi = res[1];
        res = /\+([0-9]+)/.exec(n);
        if(res) add = res[1];
      }
      var coll = new Collection();
      for( var i=0,elt; elt = this.collection[i];i++ ){
        if(i>=add){  
          // odd
          if(multi===0 && (i+1)%2 > 0){
            coll.collection.push(elt);
          // even, 3n ...
          }else if( (i+1)%multi === 0){
            coll.collection.push(elt);
          }
        }
      }
     return coll;
    }
  }
}


select('li')
//.fn('addEventListener', 'click' , alert.bind(null,'yolo') )
.fn('setAttribute', 'style' , 'cursor:pointer;color:red' )
//.nth(1).setAttribute('style','color:blue');
.nth('3n').fn('setAttribute', 'style' , 'color:blue' )
.each(function(i){t(this.innerHTML,i)});