Keeping Cookies Soft

I have this big jar for cookies. Anytime my kids want to eat one they can just grab the jar and pick up those cookies, but there is one problem that bothers me. Sometimes the cookies can get hard inside the jar, and my kids will not eat those cookies anymore. One tip I can share with you guys is to get one slice of sandwich bread and put it inside the jar together with your cookies. This time the air inside the jar that causes the cookies to get hard will be absorbed by the bread! Even after 2 days the cookies are still soft.