How to send array to node from js?

Question

JavaScript

I make a POST request, and there is a json line in it, which should go to the node and already be written to the json document there,
it looks like this:

postJson(data){
            return fetch('todo.json', {
                method: 'POST',
                body: JSON.stringify(data),
                headers: {
                    'Content-Type': 'application/json'
                }
            })
              .then(response => {response.json()})
              .then(function(response) {
                  console.info('fetch()', response);
              });
                
        },

this.postJson(this.todos)
            .then(()=>{
              console.log(this.todos)
            })

the problem is that I don't know how to access the passed data in node, and whether it's possible at all.
Please tell me what needs to be done?