Many people have started baking a recipe before and suddenly realized that they do not have enough eggs, if not any.
Fortunately, there are a few solutions to that. In place of one egg, you can add one banana. You could also add one tablespoon of applesauce, or 1/4 cup of flavorless oil, such as vegetable oil.
For substitutions with a banana, note that these taste better in chocolate recipes compared to vanilla. Using a flavorless oil will not add additional flavor, so this is a good alternative to using bananas or applesauce.
Note: these substitutions may not work in every recipe. You may need to change measurements in certain recipes.