How to push each object value into array from json?

I have a JSON response with key-values like:

....
    "usp-custom-90":"45.45257926613316,9.178168599999935"
....

Note usp-custom-90has dash!

I need something like (fields doens't exist, it's just an example):

            data.forEach(({fields})=>{
              coordsB.push(
                ...fields['usp-custom-90']
              );
            });

Where coordsB is an array defined before.

The json would be:

],
      "usp-custom-90":"45.47841306255037,9.120865849999973",
      "_links":{  
         "self":[  
            {  
               "href":"https:\/\/www.example.it\/wp-json\/wp\/v2\/posts\/128402"
            }
         ],
         "collection":[  
            {  
               "href":"https:\/\/www.example.it\/wp-json\/wp\/v2\/posts"
            }
         ],
         "about":[  

I need to push the value of each "usp-custom-90"

Full code (wrong as it is using fields which doesn't exist):

    fetch('https://www.example.it/wp-json/wp/v2/posts?per_page=50&status=publish')
      .then(res => res.json())
      .then(data =>{
        var coordsB = [];
        console.log(data);
        data.forEach(({fields})=>{
          coordsB.push(
            ...fields['usp-custom-90']
          );
        });