JavaScript If Else JavaScript If Else is used to implement conditional programming. When you start doing these things inline, it can cause page stability issues, in addition to duplicate code and potential long term headaches for the developers involved due to the manual nature of inline JavaScript. If the age is less than 18, we are going to print two statements. Hide or show elements in HTML using display property. Usually, CSS is written in a separate CSS file (with file extension .css) or in a