New line in JavaScript alert box

As of ECMAScript 2015 you can use back-ticks (` `) to enclose Template Literals for multi-line strings like this:

alert(`Line1
Line2`);

Outputs:

Line1
Line2

You can use \n for new line

alert("Welcome\nto Jumanji");

alert("Welcome\nto Jumanji");

In JAVA app, if message is read from "properties" file.

Due to double compilation java-html,

you'll need double escape.

jsp.msg.1=First Line \\nSecond Line

will result in

First Line
Second Line