proto01.js

function NewProto() {};
NewProto.prototype = {
  pull: function(data) {
    return $.ajax("ajax.php", {
      data: data, 
      type: "POST",
      context: this.el,
    });
  },
  fill: function(params) {
    if (arguments.length === 2 && typeof(params[1]) == "object") {
      this.el = params[0];
      this.data = params[1] || {};
    }
  }
};
var req = new NewProto();

$(".add2basketq").keyup(function(){
  var val = $(this).val();
  var el = $(this);
  //var bid, bpid, start, limit, price ...;
  req.fill([el, {val:val, pid:pid, bpid:bpid, ... }]);
  if (Number(val) == 0) {
    req.pull('&subaction=delete&id='+bpid+'&bpid='+bpid).
      done(function(result) {
        var output = JSON.parse(result);
        var sum1 = output.total;
        sum1 = sum1.toString().replace(/(\d)(?=(\d\d\d)+([^\d]|$))/g, '$1 ');
        if (req.query != undefined) {
          //...
        }
      });
  }
  else if (parseInt(val) <= parseInt(limit)) {
    req.pull('&action=ADD2BASKET&quantity='+val+'&id='+pid).done(function() { ... });
  }
  else {
    req.pull('&action=ADD2BASKET&quantity='+limit+'&id='+pid).done(function() { ... });
  }
});