Javascript滑块：未捕获TypeError：无法设置属性＆＃39; className＆＃39;未定义的

Question

我对此很陌生，如果有人能够解释，我真的很感激：

为什么我会收到Uncaught TypeError：无法设置属性＆＃39; className＆＃39;未定义的代码如下？

require(
["jquery"],
function($) {

    function Slider() {

        this.slides = document.querySelectorAll('#slides .slide');          
        this.currentSlide  = 0;
        this.slideInterval = 0;

    }

    Slider.prototype.startSlider = function( slideDuration ) {
        this.slideInterval = setInterval( this.nextSlide, slideDuration );
    };

    Slider.prototype.nextSlide = function() {

        this.slides[ this.currentSlide ].className = 'slide';
        this.currentSlide = ( this.currentSlide+1 ) % this.slides.length;
        this.slides[ this.currentSlide ].className = 'slide showing';           

    };

    Slider.prototype.goToThis = function() {

    };

    Slider.prototype.goToNext = function() {

    };

    Slider.prototype.goToPrev = function() {

    };

    var slider = new Slider();
    slider.startSlider( 1000 );

});

当我没有Slider（）类时，它可以正常工作。

var slides = document.querySelectorAll('#slides .slide');
var currentSlide = 0;
var slideInterval = setInterval(nextSlide,2000);

function nextSlide() {
    slides[currentSlide].className = 'slide';
    currentSlide = (currentSlide+1)%slides.length;
    slides[currentSlide].className = 'slide showing';
}

Answer 1

看起来setInterval创建了自己的上下文。尝试：

setInterval( this.nextSlide.bind(this), slideDuration );