const myString = ``;
If you want to make a multi-line string, all you need to do is wrap the string using tick quotes instead of the more common single or double-quotes. The best way to see it in action is to use the tool above. This will give you a line of code that you can copy and paste into your application.
On a qwerty keyboard, you will find the tick character ( ` ) to the left of the number 1 key and below the escape key. There will be variations depending on the keyboard manufacturer, but generally, this is where you are more than likely going to find this character.