JS-文件base64、File、Blob、ArrayBuffer互转

二进制互转

1. file对象转base64

   let reader = new FileReader();
   reader.readAsDataURL(file[0])
   console.log(reader)

2. base64 转成blob 上传

   function dataURItoBlob(dataURI) {  
       var byteString = atob(dataURI.split(',')[1]);  
       var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];  
       var ab = new ArrayBuffer(byteString.length);  
       var ia = new Uint8Array(ab);  
       for (var i = 0; i < byteString.length; i++) {  
           ia[i] = byteString.charCodeAt(i);  
       }  
       return new Blob([ab], {type: mimeString});  
   }

3. blob 转成ArrayBuffer

   let blob = new Blob([1,2,3,4])
   let reader = new FileReader();
   reader.onload = function(result) {
       console.log(result);
   }
   reader.readAsArrayBuffer(blob);

4. buffer 转成blob

   let blob = new Blob([buffer])

5. base64 转 file

   const base64ConvertFile = function (urlData, filename) { // 64转file
     if (typeof urlData != 'string') {
       this.$toast("urlData不是字符串")
       return;
     }
     var arr = urlData.split(',')
     var type = arr[0].match(/:(.*?);/)[1]
     var fileExt = type.split('/')[1]
     var bstr = atob(arr[1])
     var n = bstr.length
     var u8arr = new Uint8Array(n)
     while (n--) {
       u8arr[n] = bstr.charCodeAt(n);
     }
     return new File([u8arr], 'filename.' + fileExt, {
       type: type
     });
   }