Node-fetch problems with POST requests

You need to await for json.

var sentiments = await fetch(SEN_URL, {method: "POST", body: {"data": [{"text": "I love you"}, {"text": "I hate you"}]}})
//Here 
await sentiments.json()

Also you can make request with JSON.stringify() for body. And it will be easier to manage your js object. Like this:

var data = {data: [{text: "I love you"}, {text: "I hate you"}]};
var body = JSON.stringify(data);
var sentiments = await fetch(SEN_URL, { method: "POST", body: body });