//**dataURL to blob**
function dataURLtoBlob(dataurl) {
	debugger
	var arr = dataurl.split(‘,‘), mime = arr[0].match(/:(.*?);/)[1],
		bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
	while (n--) {
		u8arr[n] = bstr.charCodeAt(n);
	}
	return new Blob([u8arr], { type: mime });
}

//**blob to dataURL**
function blobToDataURL(blob, callback) {
	var a = new FileReader();
	a.onload = function (e) { callback(e.target.result); };
	a.readAsDataURL(blob);
}



 var _file = dataURLtoBlob(c); // c就是base64字符串

//Blob_test();
function Blob_test(){
	var blob;
	if(!window.Blob)
		console.log(‘不支持‘);
	else
		blob = _file;
	if(window.URL){
		document.getElementById("mybody").innerHTML = ‘<a download href="‘ + window.URL.createObjectURL(blob) + ‘" target="_blank">文件下载</a>‘;
	}
}

Blob_test()

var form = new FormData()
form.append(‘signature‘, this.ossData.signature)
form.append(‘accessKey‘, this.ossData.accessKey)
form.append(‘policy‘, this.ossData.policy)
form.append(‘key‘, key)

var _fileBlob = dataURLtoBlob(base64) // c就是base64字符串
form.append(‘file‘, _fileBlob)

var req = new XMLHttpRequest()
req.open(‘post‘, this.actionUrl, false)
req.send(form)