Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking dish or line it with parchment paper.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the chocolate chips and rainbow sprinkles gently until evenly distributed.
Spread the cookie dough evenly in the prepared baking dish.
Bake for 25-30 minutes, or until the edges are golden and a toothpick inserted in the center comes out clean.
Allow the cookie cake to cool in the pan for about 10 minutes before slicing into squares.