$.widget("my.idautocomplete", $.ui.autocomplete, {

    options: {
        id:""
    },

    select:function f1(event, ui) {
        this.options.id=ui.id
        console.log("Autocomplete sel " + $(this).attr("id"));
    }
}

$("input").idautocomplete({select:function f2(){alert(1);} });

$.widget("my.idautocomplete", $.ui.autocomplete, {

    options: {
        oldselect:{},
        id:""
    },
    _create: function () {
        $.ui.autocomplete.prototype._create.call(this);

        this.options.oldselect=this.options.select;
        this.options.select=this.sel;
    },

    sel:function (event, ui) {
        console.log("Autocomplete sel " + $(this).attr("id"));
    }
}

$("input").idautocomplete({select:function f2(){alert(1);} });