我想上传一个图像到Firebase存储从一个可调用的https云函数，但我不知道如何做。

const functions = require('firebase-functions');

const admin = require('firebase-admin');

admin.initializeApp();

const storageBucket = admin.storage().bucket('gs://xxxxx.appspot.com');

exports.test_upload = functions.https.onRequest(async (request, response) => {

    var base64Img = "data:image/jpeg;base64,/9j/4AAQSkZJRg...AoNDQoIC";

    let filename = new Date().getTime() + '.jpg';

    await storageRef.child('/destination/'+filename).putString(base64Img, 'data_url').then(function(snapshot) {

        snapshot.ref.getDownloadURL().then(async (url) => { 
            
            console.log(url);

        });

    });


    response.status(200).send("Done!");

});

你能帮我理解吗，怎么做？

太谢谢你了