Retrieve JSON data from the BaseCRM API and add it to a Google Sheet. This example retrieves all users. Stands on the shoulders of https://gist.github.com/varun-raj/5350595a730a62ca1954

google-script-basecrm-api.js

function getBaseUsers() {
  var options = {
   "contentType" : "application/json",
   "headers" : {
     "Accept": "application/json",
     "Authorization": "Bearer <TOKEN>"
   }
  }
  var response = UrlFetchApp.fetch("https://api.getbase.com/v2/users", options);
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheets = ss.getSheets();
  var sheet = ss.getSheetByName("baseUsers"); // specific sheet name; alternatively use ss.getActiveSheet()

  var dataAll = JSON.parse(response.getContentText()); //
  var dataSet = dataAll.items; // "items" is the key containing relevant objects
  
  var rows = [],
    data;
  
  for (i = 0; i < dataSet.length; i++) {
  data = dataSet[i];
  rows.push([data.data.id, data.data.name, data.data.email]); //your JSON entities here
  }
  
  // [row to start on], [column to start on], [number of rows], [number of entities]
  dataRange = sheet.getRange(2, 1, rows.length, 3);
  dataRange.setValues(rows);

}

Instead of having a predefined sheet name, just return rows after the for-loop so the user can descide where the data should be located...

for (i = 0; i < dataSet.length; i++) {
TypeError: Cannot read property "length" from undefined

I'm getting the same error as @linglung. Can anyone help?

@linglung for anyone struggling item is the name of the key that contain all the objects in your JSON (not the same for all APIs). Or that the URL to fetch is not breaking line and not returning anything to data (so length indefined).