我一直收到“未捕获的ReferenceError：未定义imgArray”错误

Question

I have written some code as an object to fade in and out some images, only when I call for the slideshow to be build, I am getting an

"Uncaught ReferenceError: imgArray is not defined".

Can anyone help as to why I am getting this error. Thank you.

const slideShow = {
  curIndex: 0,
  imgDuration: 10000,
  slider: document.querySelector('.banner__slider').childNodes,

  imgArray: [
    'images/background/img3.jpg',
    'images/background/img1.jpg',
    'images/background/img2.jpg'
  ],

  buildSlideShow(arr) {
    for (i = 0; i < arr.length; i++) {
      const img = document.createElement('img');
      img.src = arr[i];
      slider.appendChild(img);
    }
  },

  slideShow() {

    function fadeIn(e) {
      e.className = "fadeIn";
    };

    function fadeOut(e) {
      e.className = "";
    };

    fadeOut(slider[curIndex]);
    curIndex++;
    if (curIndex === slider.length) {
      curIndex = 0;
    }

    fadeIn(slider[curIndex]);

    setTimeout(function () {
      slideShow();
    }, imgDuration);
  },
}; 

slideShow.buildSlideShow(imgArray).slideShow();

Answer 1

You are getting the error because there is no imgArray variable in the code. You could change this to:

slideShow.buildSlideShow(slideShow.imgArray).slideShow();

This fixes one issue but creates another one. The buildSlideShow method doesn't return anything. So, .slideShow() method will again throw an error. Since, imgArray is a property of slideShow object, you can make use of the this keyword. Change the method to:

buildSlideShow() {

  for (i = 0; i < this.imgArray.length; i++) {
    const img = document.createElement('img');
    img.src = this.imgArray[i];
    slider.appendChild(img);
  }

  return this;
}

From the buildSlideShow , return the instance of the object by using return this . This way you can chain the methods.

 const slideShow = { curIndex: 0, imgDuration: 10000, // slider: document.querySelector('.banner__slider').childNodes, imgArray: [ 'images/background/img3.jpg', 'images/background/img1.jpg', 'images/background/img2.jpg' ], buildSlideShow() { console.log("inside buildSlideShow method"); for (i = 0; i < this.imgArray.length; i++) { console.log(this.imgArray[i]); const img = document.createElement('img'); img.src = this.imgArray[i]; //slider.appendChild(img); } return this; }, slideShow() { console.log("inside slideShow method") } } slideShow.buildSlideShow() .slideShow(); 

(I have commented out the slider code)

Answer 2

imgArray is not a global variable its property of the Object slideShow . You should pass slideShow.imgArray to the function

slideShow.buildSlideShow(slideShow.imgArray).slideShow();

And also fix the type missing b in start of uildSlideShow(arr){...} . It should be buildSlideShow(arr){...}