Preheat the oven to 350°F (175°C). Grease a 9x13 inch baking dish.
In a large mixing bowl, combine the mashed bananas and melted butter.
Add granulated sugar, eggs, and vanilla extract to the banana mixture, mixing until well combined.
In a separate bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry mixture to the wet ingredients, stirring gently until just incorporated.
Fold in the semi-sweet chocolate chips, ensuring even distribution throughout the batter.
Pour the batter into the prepared baking dish and smooth the top with a spatula.
Bake for 25-30 minutes, or until a toothpick inserted comes out with a few moist crumbs.
Let the bars cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely before cutting into squares.