In ES6 multiline string value can be written with backticks:
const multiline = `this is a multiline string`;
There are 2 ways how to do it. The first one is to escape newlines:
var multiline = 'This \ is\ a \ multiline \ string';
This method is not recommended. The second way, which is s recommended one, is to concatenate strings:
var multistring = 'This' + 'is ' + 'a new ' + 'multiline ' + 'string';
Don’t forget to write empty symbol (whitespace) before quotes if you want to have spaces between words.