Script to get the downloadURL via Admin SDK; if the Firebase metadata required doesn't exists, it adds it

admin_storage.js

const admin    = require('firebase-admin');
const createUuid = require('uuid-v4');

// assumes the existance of the GOOGLE_APPLICATION_CREDENCIAL env variable
admin.initializeApp({
    credential: admin.credential.applicationDefault(),
    storageBucket: '<YOUR_STORAGE_BUCKET>.appspot.com'
});

// it will get the list of files under "images" and create a downloadUrl for each one
const storage = admin.storage();
storage.bucket().getFiles({prefix: "images"})
    .then(([files]) => {
        files.forEach(async file => {
            let url = await getDownloadURL(file);
            console.log(url);
        });
    })
    .catch(err => {
        console.error(err);
    });

// methods

// build the downloadURL using the file infomation; adds the download token if it doesn't exists
async function getDownloadURL (fileRef) {
    const bucket = fileRef.bucket.name;
    const [metadata] = await fileRef.getMetadata();
    let downloadToken;

    if (!metadata.metadata) {
        console.log("NO");
        downloadToken = await setFirebaseMetadata(fileRef);
    } else {
        console.log("YES");
        downloadToken = metadata.metadata.firebaseStorageDownloadTokens.split(',')[0];
    }

    let url = `https://firebasestorage.googleapis.com/v0/b/${bucket}/o/${encodeURIComponent(fileRef.name)}?alt=media&token=${downloadToken}`;

    return url;
} // getDownloadURL

// set the Firebase metadata with the downloadToken
async function setFirebaseMetadata (fileRef) {
    let downloadToken = createUuid();
    const metadata = {
        metadata: {
            firebaseStorageDownloadTokens: downloadToken
        }
    };

    let [response] = await fileRef.setMetadata(metadata);

    return downloadToken;

} // setFirebaseMetadata

Typescript version using uuid package:

// getDownloadUrl.ts


import {v4 as uuidv4} from "uuid";
import {File} from "@google-cloud/storage";

export async function getDownloadURL (fileRef: File): Promise<string> {
    const bucket = fileRef.bucket.name;
    const [metadata] = await fileRef.getMetadata();
    let downloadToken;

    if (!metadata.metadata) {
        downloadToken = await setFirebaseMetadata(fileRef);
    } else {
        downloadToken = metadata.metadata.firebaseStorageDownloadTokens.split(',')[0];
    }

    return `https://firebasestorage.googleapis.com/v0/b/${bucket}/o/${encodeURIComponent(fileRef.name)}?alt=media&token=${downloadToken}`;
} // getDownloadURL

// set the Firebase metadata with the downloadToken
async function setFirebaseMetadata (fileRef: File): Promise<string> {
    const downloadToken = uuidv4();
    
    const metadata = {
        metadata: {
            firebaseStorageDownloadTokens: downloadToken
        }
    };

    await fileRef.setMetadata(metadata);

    return downloadToken;
} // setFirebaseMetadata