unexpected token 0 in json at position 1 code example

Example 1: "SyntaxError: Unexpected token o in JSON at position 1

var newData = JSON.stringify(userData)

Example 2: fetch SyntaxError: Unexpected token < in JSON at position 0

JSON.parse(theStringThatIsNotJson);

Example 3: unexpected token s in json at position 0

var s = '"something"';
var result = JSON.parse(s);