1 The code is not very high-level and written very low-level (prone to bugs)
2 Because the input value of a component is not cleared or some values are not initialized
3 Because the CSS style is not well written, the disable button gives both the disabled class and the disabled attribute. In fact, writing styles in CSS with attributes can easily cause the button to be grayed out but still clickable.
4 Some interactions or business logic sequence is not clear
5 Sometimes courageous, shy, or misjudgmental, dare not to do it, dare not to ask