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How does JavaScript use DOM to switch images?

不言Original: 2018-07-21 09:54:012503browse

This article shares with you how to use JavaScript to switch images using DOM? , the content is very good, friends in need can refer to it, I hope it can help everyone.

Start learning DOM operations today. Let’s write a small case to consolidate the knowledge points.

DOM: document object model

According to id Get page elements: For example: var xx = document.getElementById("id");

Get elements based on tag: For example: var xx = document .getElementsB##yTagName("p");

src="imgs/1.png"/><br>    <button id="btn1" type="button" value="

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        #outer {
            width: 500px;
            /*设置上边距50px 水平居中*/
            margin: 50px auto;
            /*设置边框*/
            padding: 10px;
            background-color: greenyellow;
            /*设置文本居中*/
            text-align: center;
        }

        img {
            width: 500px;
        }
    </style>


    <script>
　　　　　//btn 为按钮id   clickEventFunction 为点击后执行的操作函数
        function addClick(btn, clickEventFunction) {
            var myButton = document.getElementById(btn);
            myButton.onclick = clickEventFunction;
        };

        window.onload = function () {
            (function () {
                var pics = ["imgs/1.png",
                    "imgs/2.png",
                    "imgs/3.png"];
                var index = 0;
                showPicNum(index);
                var img = document.getElementsByTagName("img")[0];

                // var btn1 = document.getElementById("btn1");
                var btn2 = document.getElementById("btn2");
                addClick("btn1", function () {
                    index--;
                    if (index <= -1) {
                        index = pics.length - 1;
                    }
                    console.log(index + " ----- ");
                    img.src = pics[index];
                    showPicNum(index);
                });
                addClick("btn2", function () {
                    index++;
                    if (index >= pics.length) {
                        index = 0;
                    }
                    console.log(index + " ++++++++ ");
                    img.src = pics[index];
                    showPicNum(index);
                });

                //
                // btn1.onclick = function () {
                //     index --;
                //     if(index <= -1){
                //         index = pics.length - 1;
                //     }
                //     console.log(index  + " ----- ");
                //     img.src = pics[index];
                //     showPicNum(index);
                // };
                // btn2.onclick = function () {
                //     index ++;
                //     if(index >= pics.length){
                //         index = 0;
                //     }
                //     console.log(index  + " ++++++++ ");
                //     img.src = pics[index];
                //     showPicNum(index);
                // };
                console.log(index);

                /**
                 * 展示当前图片为第几张
                 * @param index   当前图片索引
                 */
                function showPicNum(index) {
                    var descrs = document.getElementById("discs");
                    descrs.innerText = "一共" + pics.length + "张图片,当前第" + ++index + "张";
                }
            }())
        };
    </script>
</head>
<body>
<div id="outer">
    <p id="discs"></p>
    <img src="imgs/1.png"/><br>
    <button id="btn1" type="button" value="上一张">上一张</button>
    <button id="btn2" type="button" value="下一张">下一张</button>
</div>
</body>
</html>

Document directory:

The effect is as follows:

上一张">上一张</button>    <button id="btn2" type="button" value="下一张">下一张</button></div></body></html>

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