JS文件base64、File、Blob、ArrayBuffer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); //reader.readAsArrayBuffer(blob,{type:'application/vnd.ms-excel'})

4. buffer 转成blob

let blob = new Blob([buffer])

5. base64 转 file

import {atob} from “atob”
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
  });
}

http://www.webtoolkit.info/javascript-base64.html第三方实现的 Base64 编码工具，完美的支持 unicode 编码的字符串。

> Base64.encode('中文')
"5Lit5paH"
 
> Base64.decode('5Lit5paH');
"中文"