HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="./style.css"/>
</head>
<body>
<div class="load-body">

    <div class="wrapper">
        <header>File Uploader JavaScript</header>
        <form action="#">
            <input class="file-input" type="file" name="file" hidden>
            <i class="fas fa-cloud-upload-alt"></i>
            <p>Browse File to Upload</p>
        </form>
        <section class="progress-area"></section>
        <section class="uploaded-area"></section>
    </div>


</div>
</body>
<script src="./jquery.js"></script>
<script src="./script.js"></script>
</html>

JS

const form = document.querySelector("form"),
fileInput = document.querySelector(".file-input"),
progressArea = document.querySelector(".progress-area"),
uploadedArea = document.querySelector(".uploaded-area");

// form click event
form.addEventListener("click", () => {
    fileInput.click();
});

fileInput.onchange = ({target}) => {
let file = target.files[0]; //getting file [0] this means if user has selected multiple files then get first one only
var data = new FormData();
data.append('avatar', file);
$.ajax({
        url: 'http://127.0.0.1:5000/file_uploader',
        type: 'POST',
        data: data,
        cache: false,
        processData: false,
        contentType: false,
        success: function(data, textStatus) {
            progressArea.innerHTML = "";
            let uploadedHTML = `<li class="row">
                                   ${file.name}上传完成 -> ${data}
                          </li>`;
            // uploadedArea.innerHTML = uploadedHTML; //uncomment this line if you don't want to show upload history
            uploadedArea.insertAdjacentHTML("afterbegin", uploadedHTML);
        }
    },
)
}

CSS


.load-body{
  height: 1000px;
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Poppins", sans-serif;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background: #6990F2;
}


::selection{
  color: #fff;
  background: #6990F2;
}
.wrapper{
  width: 430px;
  background: #fff;
  border-radius: 5px;
  padding: 30px;
  box-shadow: 7px 7px 12px rgba(0,0,0,0.05);
}
.wrapper header{
  color: #6990F2;
  font-size: 27px;
  font-weight: 600;
  text-align: center;
}
.wrapper form{
  height: 167px;
  display: flex;
  cursor: pointer;
  margin: 30px 0;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  border-radius: 5px;
  border: 2px dashed #6990F2;
}
form :where(i, p){
  color: #6990F2;
}
form i{
  font-size: 50px;
}
form p{
  margin-top: 15px;
  font-size: 16px;
}

section .row{
  margin-bottom: 10px;
  background: #E9F0FF;
  list-style: none;
  padding: 15px 20px;
  border-radius: 5px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

Flask

@app.route("/file_uploader", methods=["POST"])
def read_asset():
    # 获取普通参数
    print(f"request.values: {request.values}")
    print(f"request.values.get('name'): {request.values.get('name')}")
    
    # 获取文件类型的参数
    print(f"request.files: {request.files}")
    print(f"request.files.get('avatar'): {request.files.get('avatar')}")
    # 获取上传文件的二进制流
    print(f"request.files.get('avatar').read(): {request.files.get('avatar').read()}")
    # request.files["avatar"].stream.read()
    return "sesscs"

if __name__ == '__main__':
    app.run()