Preheat oven to 350°F. Line a 9×13-inch baking dish with parchment paper, then spray with nonstick cooking spray. Set aside.
Using a hand mixer, combine the butter and brown sugar in a large bowl.
On low speed, add the vanilla and mix until incorporated.
Add the eggs, mixing on low until incorporated.
Add the flour and the salt, mixing well.
Fold in the mashed bananas and chocolate chips.
Pour the batter into the prepared pan and bake for 35-40 minutes, or until the edges are golden brown and the center is set.
Once baked, let the bars cool for about 15 minutes before cutting and serving.