case：本地上传图片后实现预览与删除功能

效果预览

1.html文件

<div class="upload-box">
	<!--多选-->
  <input type="file" id="upload-Input" accept="image/*" multiple>
  <div class="upload-file">
    <div id="imagesContainer"></div>
    <button id="upload-btn">
      <img src="./add.png" alt="" width="36px" height="36px">
      <div class="tips">添加附件</div>
    </button>
  </div>
</div>
<button class="upload-submit" onclick="submit()">提交</button>

2. css文件

input[type="file"] {
  display: none;
}

button{
  width: 120px;
  height: 120px;
  background: #FFFFFF;
  border: 1px solid #0062FF;
  font-size: 16px;
  color: #0062FF;
  padding: 0;
  cursor: pointer;
}

button .tips{
  margin-top: 7px;
}

button.upload-submit {
  width: 120px;
  height: 40px;
  margin-top: 20px;
  background: #0062FF;
  border-radius: 8px;
  color: #FFFFFF;
  font-weight: 500;
  font-size: 14px;
}

.upload-file{
  display: flex;
  /* flex-wrap: wrap; */
}
.upload-file #imagesContainer{
  display: flex;
  flex-wrap: wrap;
}

.upload-box{
  width: 800px;
  background-color: #f9f9f9;
}

.upload-file .upload-item{
  width: 120px;
  height: 120px;
  position: relative;
  text-align: center;
  line-height: 120px;
  margin-right: 10px;
  margin-bottom: 10px;
}

.upload-file .upload-item .previewImg{
  max-width: 100%;
}

.upload-file .upload-item .delImg{
  position: absolute;
  right: 0;
  top: 0;
  cursor: pointer;
}

3. js文件

const uploadInput = document.getElementById('upload-Input')
const uploadBtn = document.getElementById('upload-btn')
let files = []

uploadBtn.addEventListener('click', function () {
  ()
})

uploadInput.addEventListener('change', function (e) {
  files = [...e.target.files];  
  const container = document.getElementById('imagesContainer');  
  for (let i = 0; i < files.length; i++) {  
    const file = files[i];  
    const reader = new FileReader();  
    // FileReader对象可以异步读取存储在开发者的计算机磁盘上的数据内容，可以使用File对象或Blob对象来指定所要处理的文件或数据。
    // 文件读取是异步的，因此我们不能立即访问文件内容。相反，我们需要在onload事件处理函数中处理文件内容。
    reader.onloadend = function(event) {
      // 当文件读取完成后，onload事件处理函数将被调用
      let div = document.createElement('div');  
      div.classList.add('upload-item');  

      let img1 = document.createElement('img'); 
      img1.src = reader.result;  
      // 文件内容可以通过event.target.result访问
      img1.classList.add('previewImg');   
      img1.style.maxWidth = '100%';

      let img2 = document.createElement('img');  
      img2.src = "./del.png";  
      img2.classList.add('delImg');
      img2.style.width = '16px';
      img2.style.height = '16px';
      img2.setAttribute('data_idx', i)
      img2.onclick = handleDel(i)

      div.appendChild(img1);     
      div.appendChild(img2);     
      container.appendChild(div);    
    }  

    if (file) {  
      reader.readAsDataURL(file);  
      // readAsDataURL()方法则可以将文件读取为一段以data:url格式的字符串，这段字符串的实质都是Data URI,
    }  
  } 
})
// 删除
function handleDel(idx) {
  return () => {
    const container = document.getElementById('imagesContainer'); 
    const divs = document.getElementsByClassName('upload-item'); 
    const imgdels = document.getElementsByClassName('delImg');

    for (let i = 0; i < files.length; i++) { 
      if(imgdels[i]){
        if(idx == imgdels[i].getAttribute('data_idx')){
          files.splice(i, 1)
          container.removeChild(divs[i]); 
        }     
      } 
    }  
  } 
}

function submit(){
  console.log(files.map(item => ))
}