分别到达最后一张和第一张幻灯片后，如何使“下一个”按钮和“上一个”按钮不起作用？

Question

我的幻灯片播放有问题。 我正在使用w3.js javascript，并且很好奇要添加到代码中，以停止按钮在最后一张和第一张幻灯片上的工作。 我在那里找了很多例子，但没有一个对我有用。

JS

w3.slideshow = function (sel, ms, func) {
    var i, ss, x = w3.getElements(sel),
        l = x.length;
    infinite: false;
    ss = {};
    ss.current = 1;
    ss.x = x;
    ss.ondisplaychange = func;
    if (!isNaN(ms) || ms == 0) {
        ss.milliseconds = ms;
    } else {
        ss.milliseconds = 1000;
    }
    ss.start = function () {
        ss.display(ss.current)
        if (ss.ondisplaychange) {
            ss.ondisplaychange();
        }
        if (ss.milliseconds > 0) {
            window.clearTimeout(ss.timeout);
            ss.timeout = window.setTimeout(ss.next, ss.milliseconds);
        }
    };
    var clicks = 1;
    ss.next = function () {
        infinite: false;
        ss.current += 1;
        if (ss.current > ss.x.length) {
            ss.current = 1;
        }
        ss.start();
    };
    ss.previous = function () {
        infinite: false;
        ss.current -= 1;
        if (ss.current < 1) {
            ss.current = ss.x.length;
        }
        ss.start();
    };
    ss.display = function (n) {
        w3.styleElements(ss.x, "display", "none");
        w3.styleElement(ss.x[n - 1], "display", "block");
    }
    ss.start();
    return ss;
};

的HTML

<div class="note">
    <h1>4Nadpis elearningu</h1>
    <p>4Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec ornare ut sem at lobortis. Integer mattis venenatis enim eget semper. Integer finibus, augue a venenatis consequat, odio purus porta odio, in lobortis velit libero eget nunc. Nunc purus nisi, mollis ac facilisis sed, varius ut ipsum. Donec elementum sagittis elit, quis pellentesque risus lobortis vel. In et erat consequat, vestibulum felis et, luctus urna. Aliquam ipsum elit, varius fermentum rutrum eget, lobortis non purus. Nulla id nunc viverra nisi porttitor fermentum ut eu diam. In at vestibulum quam. Aenean non eros erat. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam ornare convallis lacus, vel dictum nibh convallis sed. Phasellus sem arcu, posuere id blandit ac, placerat dignissim erat. In congue lorem id vestibulum consequat. Proin feugiat ligula nec velit viverra commodo. Donec vitae maximus felis.</p>
</div>
<div class="note">
    <h1>5Nadpis elearningu</h1>
    <p>5Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec ornare ut sem at lobortis. Integer mattis venenatis enim eget semper. Integer finibus, augue a venenatis consequat, odio purus porta odio, in lobortis velit libero eget nunc. Nunc purus nisi, mollis ac facilisis sed, varius ut ipsum. Donec elementum sagittis elit, quis pellentesque risus lobortis vel. In et erat consequat, vestibulum felis et, luctus urna. Aliquam ipsum elit, varius fermentum rutrum eget, lobortis non purus. Nulla id nunc viverra nisi porttitor fermentum ut eu diam. In at vestibulum quam. Aenean non eros erat. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam ornare convallis lacus, vel dictum nibh convallis sed. Phasellus sem arcu, posuere id blandit ac, placerat dignissim erat. In congue lorem id vestibulum consequat. Proin feugiat ligula nec velit viverra commodo. Donec vitae maximus felis.</p>
</div>
<br>
<button class="button" onclick="myShow.previous()">Naspat</button>
<button class="button" onclick="myShow.next()">Dalej</button>

<script>
    myShow = w3.slideshow(".note", 0);
</script>

应该停止在最后一张幻灯片上工作（“下一个”按钮），并且也停止在第一张幻灯片上工作（“上一个”按钮）。

Answer 1

下面的函数确定如果单击下一步会发生什么

  ss.next = function() {
    infinite: false;
    ss.current += 1;
    if (ss.current > ss.x.length) {ss.current = 1;}
    ss.start();
   };

可变电流跟踪当前幻灯片。 在这里，它增加了1，并且如果它大于图​​片数量-x.length ，则将其重置为1。

而不是自动递增，只需检查它是否是最后一个元素并停止递增

  ss.next = function() {
    infinite: false;
    if (ss.current + 1 <= ss.x.length) {ss.current += 1;}
    ss.start();
   };

对于以前的功能也是如此。 检查减1是否会导致大于0的数字以及是否是大小写减。

  ss.previous = function() {
    infinite: false;
    if (ss.current-1 > 0) {ss.current -= 1;}
    ss.start();
  };