Pass image files through firebase function arguments

functions>index.js

exports.uploadImage = functions.https.onCall(async (data, context) => {

    const mimeType = data.image.match(/data:([a-zA-Z0-9]+\/[a-zA-Z0-9-.+]+).*,.*/)[1];
    const base64EncodedImageString = data.image.replace(/^data:image\/\w+;base64,/, '');
    const imageBuffer = new Buffer(base64EncodedImageString, 'base64');

    const filename = `posts/${data.name}.${mimeTypes.detectExtension(mimeType)}`;
    const file = admin.storage().bucket().file(filename);
    await file.save(imageBuffer, { contentType: 'image/jpeg' });
    const photoURL = await file.getSignedUrl({ action: 'read', expires: '03-09-2491' }).then(urls => urls[0]);
    
    return { photoURL }; 
});

index.html

<input type="file" id="image-input" value="upload" accept="image/jpeg"/>
<button onclick="submit()"> Upload </button>

script.js

let base64image = '';
let reader = new FileReader();

document.getElementById('image-input').addEventListener('change', ev => {
    reader.readAsDataURL(ev.target.files[0]);
});

reader.addEventListener("load", function () {
    base64image = reader.result;
}, false);

function submit() {
    firebase.functions().httpsCallable('uploadImage')({ name: 'Image Name', image: base64image });
}