It's possible to create multiline strings in JavaScript by using a slash before a newline. Some consider this to be a bad practice as it was an undocumented feature of JavaScript that was only formalized later. Consider using template strings or concatenating the strings instead.
const x = "Line 1 \
Line 2";
const x = "Line 1\n" +
"Line 2";
const x_ = `Line 1
Line 2`