function 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;

}

// dataURL to blob

// 假设一个dataURL

const ImageURL = "转成Base64的变量";

// Split the base64 string in data and contentType

const block = ImageURL.split(";");

// Get the content type of the image

const contentType = block[0].split(":")[1];// In this case "image/jpeg"

// get the real base64 content of the file

const realData = block[1].split(",")[1];// In this case "R0lGODlhPQBEAPeoAJosM...."

// Convert it to a blob to upload

var blob = b64toBlob(realData, contentType);

// new a formData

const formData = new FormData();

formData.append('blob', blob);

// upload

$.ajax({

    url:url,

    data: formData

    type:"POST",

    contentType:false,

    processData:false,

    error:function(err){

    },

    success:function(data){

    },

});