wuchengwei/dataURL to blob and blob to dataURL

## dataURL to blob and blob to dataURL
//**dataURL to blob**
function dataURLtoBlob(dataurl) {
    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);
}

//test:
var blob = dataURLtoBlob('data:text/plain;base64,YWFhYWFhYQ==');
blobToDataURL(blob, function(dataurl){
    console.log(dataurl);
});
	//dataURL to blob
	function dataURLtoBlob(dataurl) {
	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);
	}

	//test:
	var blob = dataURLtoBlob('data:text/plain;base64,YWFhYWFhYQ==');
	blobToDataURL(blob, function(dataurl){
	console.log(dataurl);
	});