在滑块中不起作用.css（）方法

'use strict';
$(function () {
    var currentSlide = 1;

    //DOM cache
    var $slider = $('#slider');
    var $slidesContainer = $slider.find('#container');
    var $slides = $slidesContainer.find("li")
    console.log($slides.length);


    //slider
    setInterval(slide, 3000);

    function slide() {
        $slidesContainer.animate({'margin-left': '-='+400}, 800);
        console.log(currentSlide);
        currentSlide++;
        if (currentSlide === $slides.length) {
            currentSlide = 1;
            $slidesContainer.css("margin-left", 0);// <------PROBLEM HERE
        }//end if           
    }//end slide
});//end js
'use strict';
$(function () {
    var currentSl