上传图片js流程

document.getElementById('uploadButton').addEventListener('click', function() {
    const fileInput = document.getElementById('fileInput');
    const file = fileInput.files[0];
    if (!file) {
        alert('请选择一个文件');
        return;
    }

    const formData = new FormData();
    formData.append('file', file);

    const xhr = new XMLHttpRequest();
    xhr.open('POST', '/upload', true);

    xhr.upload.onprogress = function(event) {
        if (event.lengthComputable) {
            const percentComplete = (event.loaded / event.total) * 100;
            console.log(`上传进度: ${percentComplete}%`);
        }
    };

    xhr.onload = function() {
        if (xhr.status === 200) {
            console.log('上传成功:', xhr.responseText);
        } else {
            console.error('上传失败:', xhr.statusText);
        }
    };

    xhr.send(formData);
});