foden dev

Firing a function on tab/browser close

☕️ 2 min read

Firebase billed me my own $ for February ?!

Dodgeball ben stiller no one makes me bleed my own blood gif

While $0.30 is a small amount of money so not too upsetting,

screen shot of firebase console costs

this should not have happened yet since we are still in development, and increased the priority of fixing some technical debt/a larger issue with my form component. (Also a good reminder to get the boss’ credit card in place . .)

This project is on a Blaze Plan so we can run backups of the real time database, but the free tier has to be surpassed before any charges are incurred.

So how did we blow through our outgoing bandwith allowance on firebase’s free tier?

The project requirement for the form component I was building outlined that if a user leaves the page that we don’t lose all of their inputs so they can come back later and pick up the draft where they left off. I had wired it to update firebase when it updated state, easy, simple and worked well. You can probably see where this is going. This was shortsighted at best, since a database call on every key stroke was bound to add up. Having used firebase on multiple platforms with many many users, I chalked this temporary(read crappy) solution as fine since having enough users to hit the limits of the free tier would be a “high class problem”.

Not totally naive to this future/pending issue I was creating, I had taken stab at a componentWillUnmount() solution, but this doesn’t fire if a user closes the browser and so had abandoned that pursuit and in interest of shipping and picking up another story, I wired it up the aforementioned ineffcient wrong way and off we went.

Taking some time to work this weekend(No I don’t work at Revolut (zing)), I came up with a better/will be much cheaper solution for the form component.

Using the beforeunload event

Note: I am using this beforeunload without event.returnValue = '' so there is no confirm close dialogue for user to click “leave” or “close” etc

componentDidMount() {
 window.addEventListener("beforeunload", e => this.unloadUpdate(e));

unloadUpdate = e => {
  //Pseudo code starting here will need db ref and project state etc 
  //create a form object formObj here from state and update the db record
    .then(console.log("Saved your draft you lucky duck. . . but this wont show up anywhere"))
    .catch((error) => {
      console.log("You'll never get a console log since you/they are closing the browser " + error.code);

Love it? Hate it? Holler at me

— Nick