Laravel API在响应前加上npm

I have a project in Laravel 5.7.9 with an API. When I try to go to any of my routes I get an error saying

SyntaxError: JSON.parse: unexpected keyword at line 1 column 1 of the JSON data

This was previously working fine so did some testing and noticed the following:

In my routes/api.php file I created the following code

Route::get('test', function(){
    return 'my-test';
});

now when I head to mysite.sandbox/api/test I get a response saying npmtest

similarly, when i try to query the API for a JSON response I get my JSON response wrapped with npm{}

npm{"data":[{"id":324,"titulo":"...","descripcion":"...",...},{"id":323,...},{"id":320,...}],"meta":{"pagination":{"total":3,"count":3,"per_page":15,"current_page":1,"total_pages":1,"links":[]}}}

I'm not sure when this broke but I do remember doing an npm install before the error began. What could be causing this? And how can I fix this? Would appreciate any suggestions, thanks.

Update Here is another situation where npm is showing up where it's not suppose to...

$ php artisan cache:clear
npmApplication cache cleared!