>>> class attrdict(dict):
	__getattr__ = dict.__getitem__
	__setattr__ = dict.__setitem__
	__delattr__ = dict.__delitem__

	
>>> import json
>>> o = json.loads('{"foo":"bar","baz":42}', object_hook=attrdict)
>>> o.foo
'bar'

$.ajax({
  url: "ajaxTest.py",
  type: "POST",
  dataType: 'json',
  data: {foo: 'bar', baz: 42},		
  success: function(result){
    console.log(result);
  }
});

var params = new URLSearchParams()
params.set('foo', 'bar')
fetch('/handler.php', {
  method: 'POST', 
  body: params.toString(),
  headers: {
    'Content-Type': 'application/x-www-form-urlencoded'
  }
})
.then(r => r.json())
.then(data => console.log(data))

var formData = new FormData()
formData.set('name', 'Joe')
formData.set('photo', document.getElementById('photo'))
// или можно вообще var formData = new FormData(document.getElementById('post-form'))

// multipart/form-data
fetch('/handler.php', {
  method: 'POST', 
  body: formData,
})
.then(r => r.json())
.then(data => console.log(data))

// Отправляем JSON
fetch('/handler.php', {
  method: 'POST', 
  body: JSON.stringify({foo: 'bar'}), 
  headers: {
    'Content-Type': 'application/json; charset=utf-8'
  }
})
.then(r => r.json())
.then(data => console.log(data))