JavaScript Fetch Code Works in Postman, but not Google Script Editor

This JavaScript Fetch code returns the data I need in Postman. But, I am trying to get this code to work in Google Script Editor for my google sheet, and it is giving me the following error:

ReferenceError: Headers is not defined line 3.

I am brand new to coding, so please bear with me.

Any idea what's wrong here?

POSTMAN CODE:

var myHeaders = new Headers();
myHeaders.append("Content-Type", "text/plain");

var raw = "{\n    \"id\": 1,\n    \"jsonrpc\": \"1.0\",\n    \"method\": \"getbeaconbeststatedetail\",\n    \"params\": []\n}";

var requestOptions = {
  method: 'GET',
  headers: myHeaders,
  body: raw,
  redirect: 'follow'
};

fetch("https://mainnet.incognito.org/fullnode", requestOptions)
  .then(response => response.text())
  .then(result => console.log(result))
  .catch(error => console.log('error', error));

EDIT:

I have tried to update this:

       function myFunction() {
        var data = {
          'request': {
        'id': '1',
        'jsonrpc': '1.0',
        'method': 'getbeaconbeststatedetail',
        'params': []
            }
      };
      var payload = JSON.stringify(data);
      var options = {
        'method' : 'GET',
        'headers': { 'Content-Type': "text/plain", 'Accept': "text/plain"},
      'muteHttpExceptions': true,
        'contentType' : 'application/json',
        'body' : payload
      };
    
      var url = "https://mainnet.incognito.org/fullnode";
      var response = UrlFetchApp.fetch(url, options);
      var txt= response.getContentText();
      var d=JSON.parse(txt);

var sh1=SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet14"); 
for (let i = 0; i < d.length; i++) {
 sh1.getRange(1, 1).setValue(d);
}

}

But, I am still getting the following error:

Exception: Request failed for https://mainnet.incognito.org returned code 400

Solution

If you are trying to make an HTTP request from Google Apps Script, you have to use the UrlFetchApp() method.

As @Tanaike points out, GAS is based in JS but not all JS functions are allowed. However GAS does have many services to integrate with G Suite products, and external APIs or services. One very useful service is URL Fetch Service which allows you to perform any type of Http request.

For example:

// Make a GET request with headers.
var options = {
     "method" : "GET",
     "headers" : {
       "Content-Type" : "text/plain",
       "API_KEY": "dummydummy"
     }
   };
var response = UrlFetchApp.fetch("https://api.myawesomeapi.com/get", options);

You can also make POST or other requests. Please refer to the examples in the documentation for use cases.

Update:

You are receiving the 400 "Bad request" error from the "fullnode" endpoint because it requires a POST request with a payload.

function fetchFullNode() {
  var url = "https://mainnet.incognito.org/fullnode";
  
  var data = {
    "jsonrpc":"1.0",
    "method":"getblockchaininfo",
    "params":"",
    "id":65
  };
  
  var options = {
    'method' : 'post',
    'contentType': 'application/json',
    'payload' : JSON.stringify(data)
  };
  
  var response = UrlFetchApp.fetch(url, options);
  var txt= response.getContentText();
  return JSON.parse(txt);
}