react native error : Body not allowed for GET or HEAD requests

fetch("http://test.com/login.php",{
	 method  : 'GET',
		header : {
		 Accept  : 'application/json',
		'Content-Type' : 'application/json'
		},
		body :  JSON.stringify ({
		username : 'avc',
		password : 'ajad'
		})
		}). 	.done();

 node_modules\react-native\Libraries\Core\ExceptionsManager.js:65 Body not allowed for GET or HEAD requests

fetch("http://test.com/login.php",{
	 method  : 'GET',
		header : {
		 Accept  : 'application/json',
		'Content-Type' : 'application/json'
		} 
		}). 	.done();

fetch("http://test.com/login.php",{
	 method  : 'POST',
		header : {
		 Accept  : 'application/json',
		'Content-Type' : 'application/json'
		},
		body :  JSON.stringify ({
		username : 'avc',
		password : 'ajad'
		})
		}). 	.done();