Large file slice upload

Large file slice upload

Foreword
Large file slice upload mainly involves the following aspects:

1. File slicing: Divide a large file to be uploaded into multiple small files for uploading one by one.
2. File upload: Upload each small file to the server, which can be achieved using ajax, fetch, etc.
3. File merge: When all small files have been uploaded, merge them into a complete file in order. File merging can be achieved using back-end languages ​​such as Node.js.

The following is the case code

//文件切片
function sliceFile(file, chunkSize) {
    
    
  const fileSize = file.size;
  const chunks = Math.ceil(fileSize / chunkSize);

  const result = [];
  let start = 0;
  let end = chunkSize;

  for (let i = 0; i < chunks; i++) {
    
    
    if (end > fileSize) {
    
    
      end = fileSize;
    }
    const blob = file.slice(start, end);
    result.push({
    
    
      file: blob,
      start,
      end,
      index: i,
      total: chunks,
    });
    start = end;
    end = start + chunkSize;
  }

  return result;
}

//文件上传
function uploadFile(chunk) {
    
    
  const formData = new FormData();
  formData.append('file', chunk.file, `${
      
      chunk.index}-${
      
      chunk.total}`);

  return fetch('url/upload', {
    
    
    method: 'POST',
    body: formData,
  }).then((res) => res.json());
}

//文件合并
function mergeFile(chunks) {
    
    
  const formData = new FormData();
  formData.append('chunks', JSON.stringify(chunks));

  return fetch('url/merge', {
    
    
    method: 'POST',
    body: formData,
  }).then((res) => res.json());
}

//文件上传入口
function upload(file) {
    
    
  const chunkSize = 1024 * 1024 * 2; // 每个文件切片大小为2M
  const chunks = sliceFile(file, chunkSize);

  const uploadPromises = chunks.map((chunk) => {
    
    
    return uploadFile(chunk);
  });

  Promise.all(uploadPromises)
    .then(() => {
    
    
      // 所有文件上传完成，进行合并操作
      mergeFile(chunks)
        .then(() => {
    
    
          console.log('合并完成');
        })
        .catch((e) => {
    
    
          console.error('合并失败', e);
        });
    })
    .catch((e) => {
    
    
      console.error('上传失败', e);
    });
}

In the code, sliceFilethe function implements file slicing, uploadFilethe function implements file upload, and mergeFilethe function implements file merging.

uploadFunction is the entry point for file upload. It first uses sliceFilethe function to slice the large file, then uses uploadFilethe function to upload each small file in turn, and finally uses mergeFilethe function to merge all the small files into a complete file.

It should be noted that the above code is just a simple example. In actual production environment, more details need to be considered, such as network exception handling, upload speed limit, etc.