blog 上传base64图片

'use strict';

const b64toBlob = (b64Data, contentType='', sliceSize=512) => {
  const byteCharacters = atob(b64Data);
  const byteArrays = [];
  
  for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
    const slice = byteCharacters.slice(offset, offset + sliceSize);
    
    const byteNumbers = new Array(slice.length);
    for (let i = 0; i < slice.length; i++) {
      byteNumbers[i] = slice.charCodeAt(i);
    }
    
    const byteArray = new Uint8Array(byteNumbers);
    
    byteArrays.push(byteArray);
  }
  
  const blob = new Blob(byteArrays, {type: contentType});
  return blob;
}


const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';

const blob = b64toBlob(b64Data, contentType);
const blobUrl = URL.createObjectURL(blob);

const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);





var oMyForm = new FormData();

oMyForm.append("username", "Groucho");
oMyForm.append("accountnum", 123456); // 数字123456被当即转换成字符串"123456"

// fileInputElement中已经包含了用户所选择的文件
oMyForm.append("userfile", fileInputElement.files[0]);

//你还能够不借助HTML表单,直接向FormData对象中添加一个File对象或者一个Blob对象:
data.append("myfile", myBlob);

var oFileBody = '<a id="a"><b id="b">hey!</b></a>'; // Blob对象包含的文件内容
var oBlob = new Blob([oFileBody], { type: "text/xml"});

oMyForm.append("webmasterfile", oBlob);

var oReq = new XMLHttpRequest();
oReq.open("POST", "http://foo.com/submitform.php");
oReq.send(oMyForm);