When you click on the button, all checkbox inside the list element should get active. But by clicking on the button, the button disappears itself. What do I do wrong? Here is my code:When you click on the button, all checkbox insi
When you click on the button, all checkbox inside the list element should get active. But by clicking on the button, the button disappears itself. What do I do wrong? Here is my code:When you click on the button, all checkbox insi