JS basics--several ways to output messages

(1) alert() pops up a dialog box on the page, used for early JS debugging.

(2) Confirm() A dialog box pops up on the page, which is often used with if judgment.

(3) console.log() Input information to the console for js debugging.

(4) prompt() pops up a dialog box to receive information entered by the user.

(5) document.write() outputs messages on the page /*document.write can not only output information, but also output tags. */