[Vuejs]-How to use complex document text as the input variable in Vue?

The reason why it breaks is because you are not escaping the new line character.
i.e., instead of this:

var starting_point =  '# fourthwhat is this? 
;o
how bout dat. ';

Your code should look like this:

var starting_point =  '# fourthwhat is this? \
;o \
how bout dat. ';

So, if you’re getting the markdown string from an external, dynamic source, you’ll have to add the \ character before each line break.

EDIT: alternatively, you could just use the backtick operator (`):

var starting_point =  `# fourthwhat is this? 
;o
how bout dat. `;