You can check: https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code as well. underneath the paragraph: 'Why bother'

The normal order of execution of statements in a computer program is in straight-line order, from top to bottom. However, sometimes it is desirable to execute one or more statements conditionally, i.e. depending on whether some condition – determined by the state of your program – holds true (Boolean expression).