I have a Google Analytics code on my page, and it somehow finds out user's gender, age and location. Can I access that data when the user opens the page, and show something like "Hey, that's what Google knows about you: your age, gender and the city"?
I use analytics.js, just in case it's important.
Probably analytics.js has some functions in it and I can access it using JavaScript? Or that data could be found out some other way?
Google doesn't provide this data for individual users. It's only available on an aggregate basis in Analytics reports. They even apply thresholds to some reports so that individuals can't be identified.