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随机图像javascript

分类：编程问答

如何解决随机图像javascript

我对这个随机图像 javascript 有点挣扎，尽管我觉得答案很简单。我的代码一次生成四个字母（图像）。如何让代码重新生成新字母而不是添加四个额外的字母（图像）？

这里还有一个 Jsfiddle。

  <script>
function getRandomImage() {
//declare an array to store the images
var randomImage = new Array();

//insert the URL of images in array
randomImage[0] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/a.png";
randomImage[1] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/b.png";
randomImage[2] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/c.png";
randomImage[3] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/d.png";
randomImage[4] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/e.png";
randomImage[5] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/f.png";
randomImage[6] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/g.png";
randomImage[7] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/h.png";
randomImage[8] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/i.png";
randomImage[9] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/j.png";
randomImage[10] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/k.png";
randomImage[11] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/l.png";
randomImage[12] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/m.png";
randomImage[13] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/n.png";
randomImage[14] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/o.png";
randomImage[15] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/p.png";
randomImage[16] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/q.png";
randomImage[17] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/r.png";
randomImage[18] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/s.png";
randomImage[19] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/t.png";
randomImage[20] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/u.png";
randomImage[21] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/v.png";
randomImage[22] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/w.png";
randomImage[23] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/x.png";
randomImage[24] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/y.png";
randomImage[25] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/z.png";
//loop to display five randomly chosen images at once
for (let i=0; i< 4; i++) {
//generate a number and provide to the image to generate randomly
var number = Math.floor(Math.random()*randomImage.length);
//print the images generated by a random number
document.getElementById("result").innerHTML += '<img src="'+ randomImage[number] +'" style="height:150px";/>';
}
}

</script>
<body>
<h1> GENERATE YOUR LETTERS... </h1>
<!-- call user-defined getRandomImage function to generate image -->  
<center><button onclick = "getRandomImage()" class="btn btn-white btn-        animate">Let's Go!</button></center>
<br> <br>
<span id="result" align="center"> </span>

解决方法

您可以在 for 循环之前添加 document.getElementById('result').innerHTML = "" 以在添加 4 个新项目之前清除结果 div。

您还可以通过使用 for 循环生成图像 URL 来大量减少代码。

var letters = 'abcdefghijklmnopqrstuvwxyz'.split('');

for (let i = 0; i < letters.length; i++) {
    randomImage.push(`http://www.englishclass.dk/_themes/englishclass/img/scrabble/${letters[i]}.png`)
}
,

document.getElementById('result').innerHTML = " " for 循环前

    <script>
function getRandomImage() {
//declare an array to store the images
var randomImage = new Array();

//insert the URL of images in array
randomImage[0] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/a.png";
randomImage[1] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/b.png";
randomImage[2] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/c.png";
randomImage[3] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/d.png";
randomImage[4] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/e.png";
randomImage[5] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/f.png";
randomImage[6] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/g.png";
randomImage[7] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/h.png";
randomImage[8] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/i.png";
randomImage[9] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/j.png";
randomImage[10] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/k.png";
randomImage[11] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/l.png";
randomImage[12] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/m.png";
randomImage[13] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/n.png";
randomImage[14] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/o.png";
randomImage[15] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/p.png";
randomImage[16] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/q.png";
randomImage[17] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/r.png";
randomImage[18] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/s.png";
randomImage[19] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/t.png";
randomImage[20] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/u.png";
randomImage[21] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/v.png";
randomImage[22] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/w.png";
randomImage[23] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/x.png";
randomImage[24] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/y.png";
randomImage[25] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/z.png";
//loop to display five randomly chosen images at once
document.getElementById("result").innerHTML="";
for (let i=0; i< 4; i++) {
//generate a number and provide to the image to generate randomly
var number = Math.floor(Math.random()*randomImage.length);
//print the images generated by a random number

document.getElementById("result").innerHTML += '<img src="'+ randomImage[number] +'" style="height:150px";/>';
}
}

</script>
<body>
<h1> GENERATE YOUR LETTERS... </h1>
<!-- call user-defined getRandomImage function to generate image -->  
<center><button onclick = "getRandomImage()" class="btn btn-white btn-        animate">Let's Go!</button></center>
<br> <br>
<span id="result" align="center"> </span>
,

在函数定义的开头添加以下代码：

document.getElementById("result").innerHTML = "";

像这样

<script>
function getRandomImage() {

document.getElementById("result").innerHTML = "";

//declare an array to store the images
var randomImage = new Array();

//insert the URL of images in array
randomImage[0] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/a.png";
randomImage[1] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/b.png";
randomImage[2] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/c.png";
randomImage[3] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/d.png";
randomImage[4] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/e.png";
randomImage[5] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/f.png";
randomImage[6] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/g.png";
randomImage[7] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/h.png";
randomImage[8] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/i.png";
randomImage[9] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/j.png";
randomImage[10] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/k.png";
randomImage[11] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/l.png";
randomImage[12] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/m.png";
randomImage[13] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/n.png";
randomImage[14] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/o.png";
randomImage[15] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/p.png";
randomImage[16] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/q.png";
randomImage[17] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/r.png";
randomImage[18] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/s.png";
randomImage[19] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/t.png";
randomImage[20] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/u.png";
randomImage[21] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/v.png";
randomImage[22] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/w.png";
randomImage[23] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/x.png";
randomImage[24] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/y.png";
randomImage[25] = "http://www.englishclass.dk/_themes/englishclass/img/scrabble/z.png";
//loop to display five randomly chosen images at once
for (let i=0; i< 4; i++) {
//generate a number and provide to the image to generate randomly
var number = Math.floor(Math.random()*randomImage.length);
//print the images generated by a random number
document.getElementById("result").innerHTML += '<img src="'+ randomImage[number] +'" style="height:150px";/>';
}
}

</script>
<body>
<h1> GENERATE YOUR LETTERS... </h1>
<!-- call user-defined getRandomImage function to generate image -->  
<center><button onclick = "getRandomImage()" class="btn btn-white btn-        animate">Let's Go!</button></center>
<br> <br>
<span id="result" align="center"> </span>
,

如 "innerHTML += ..." vs "appendChild(txtNode)" 中所述，通过执行 innerHTML += '<img />' 追加新元素会导致浏览器重建整个容器。这可能会导致性能问题，具体取决于您调用它的位置、时间和频率。为完整起见，我提供了性能更高的示例（有点冗长，但总的来说是更好的实践）。

这应该替换您的 for 循环：

// Clear all childs from the container

const container = document.getElementById("result");
container.childNodes.forEach((child) => child.remove());

for (let i = 0; i < 4; i++) {
  const number = Math.floor(Math.random() * randomImage.length);

  // Create a new <img /> element and append it to the container

  const image = document.createElement("img");
  image.src = randomImage[number];
  image.style.height = "150px";
  container.append(image);
}
,

您还可以使用投票最多的答案 here 中给出的方法，在不拆分字符串的情况下获取随机字母。然后，您可以像上面提到的其他人一样将您的代码简化为仅几行。

我已经对下面的代码进行了注释。

// Function triggered with onclick event
function getRandomImage() {

  // Clear the previous letters
  document.getElementById("result").innerHTML = "";

  // Loop
  for (let i = 0; i < 4; i++) {

    // Generate random letter
    letter = String.fromCharCode(97 + Math.floor(Math.random() * 26))

    // Add image to #result
    document.getElementById("result").innerHTML += '<img src="http://www.englishclass.dk/_themes/englishclass/img/scrabble/' + letter + '.png" style="height:150px";/>';

  }

}
  <h1> GENERATE YOUR LETTERS... </h1>
  <center>
    <button onclick="getRandomImage()" class class="btn btn-white btn-animate">
      Let's Go!
    </button>
  </center>
  <br>
  <br>
 <span id="result" align="center"> </span>

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