var test = function(){};
testProto = test.prototype;

testProto.a = function(){
    return this;
}

testProto.b = function(){
    return this;
}
var idx = 0;
testProto.c = function(){
    console.log('call -> ' + (idx++))
    var self = this;
    setInterval(self.c.bind(self) , 1000)
}


var test = new test();
test.a().b().c();