Chop the avocado, onion, tomato, mango, and pineapple into relatlively uniform pieces (using the power of the internet for help with your mango or avocado, no judgment).
Chop the jalapeno into slightly smaller pieces.
Toss all together and stir in lime juice.
Serve immediately or store in the fridge (with minimum headspace to keep exposed avocado from browning) for up to a few hours. Leftovers can be stored in a refrigerated airtight container for a few days.
Notes
Remove the ribs and seeds from the jalapeno for a less spicy salsa; leave in if you prefer spice. Consider wearing gloves when chopping the spicy pepper.