Javascript images slide

问题

I am creating a website for my school project. I want to put some pictures in a slide show, but for some reason my code isnt working. Here is my code

   <div class="row">
     <div class="col-md-12">
       <h3 class = "Contains">
          <script type = "text/javascript">
            var image1= new image()
            image1.src=images/truck1.png

            var image2= new image()
            image2.src=images/truck4.png

            var image3= new image()
            image3.src=images/truck7.png

          </script>
          <img src="images/truck1.PNG" name = "slide" width ="400" height ="400">

          <script>
            var step =1;

            function slideit(){
              document.images.slide.src=eval("image"+step+".src");
              if (step<3)
                step++;
              else
                step=1;

              setTimeout("slideit()", 2500);
            }

            slideit()
          </script>
     </h3>
</div>

回答1:

A very basic and simple example of how you can step through an array

//Array of images
var Images = ['https://dummyimage.com/100x100/000/fff.jpg',
  'https://dummyimage.com/200x200/000/fff.jpg',
  'https://dummyimage.com/300x300/000/fff.jpg'
];
//Step counter
var step = 1;

function gallery() {
  //change image
  document.getElementById('Imgs').src = Images[step];
  //Or you can use - document.images.slide.src=Images[step];
  // is step more than the image array?
  if (step < Images.length - 1) {
    // No - add 1 for next image.
    step++;
  } else {
    // Yes - Start from the first image
    step = 0;
  }
}
//When the ready, set interval.
window.onload = setInterval(gallery, 2500);

<img id="Imgs" name="slide" src="https://dummyimage.com/100x100/000/fff.jpg" />

The method you're trying will return the following errors in the browser console.

Uncaught ReferenceError: image is not defined(anonymous function)

Uncaught TypeError: Cannot read property 'src' of undefined

The browser console is your best friend when it comes to using javascript.

If you have any questions, please leave a comment below and I will get back to you as soon as possible.

---

If you want to stick with the same method here it is:

var step = 1;
var image1 = new Image();
image1.src = "https://dummyimage.com/100x100/000/fff.jpg";
var image2 = new Image();
image2.src = "https://dummyimage.com/200x200/000/fff.jpg";
var image3 = new Image();
image3.src = "https://dummyimage.com/300x300/000/fff.jpg";

function slideit() {
  document.images.slide.src = window['image' + step].src;
  if (step < 3)
    step++;
  else
    step = 1;
  setTimeout(slideit, 2500);
}
slideit();

<div class="row">
  <div class="col-md-12">
    <h3 class="Contains">
      <img src="https://dummyimage.com/100x100/000/fff.jpg" name="slide" />
    </h3>
  </div>

I hope this helps. Happy coding!

回答2:

Your problem is most probably in your "imagex.src=xxxxxxx". The images urls are string and must be quoted as such. So it should be :

image1.src="images/truck1.png"

Also, you try to call setTimeout with a string instead of a function reference/name. It should be :

setTimeout(slideit, 2500);

However, a setInterval would be best here instead of a setTimeout as it will call a function repetingly.

JS aside, there are some quirk in the HTML part. Mostly, you shouldn't use a H3 to wrap a div. H3 are ususaly used for page sub-titles, not for a 400x400 images ^^

As mentioned in your question comments, using eval is generaly a bad idea.

To Simplify, you could do something like this :

<div class="row">
    <div class="col-md-12">
        <div class="Contains">
            <img src="images/truck1.PNG" name="slide" width="400" height="400">
            <script>
                var pictures = ["images/truck1.png",
                                "images/truck4.png",
                                "images/truck7.png"];

                var step = 0;

                function slideIt(){
                    if (step<3)
                        step++;
                    else
                        step=0;

                    document.images.slide.src=pictures[step];
                }

                setTimeout(slideit, 2500);
            </script>
        </div>
    </div>
</div>

来源：https://stackoverflow.com/questions/30372444/javascript-images-slide