AJAX REST API请求

Question

My problem is that I can not send the correct request to the server to get an answer from him in the form of a json line.
Here is my code:

$.ajax({
    type: "GET",
    url: url,
    dataType: 'json',
    crossDomain: true,
    username: 'username',
    password: 'password',
    headers: {
        'Access-Control-Allow-Origin': '*'
    },
    success: function(response) {
        console.log(response);
    }
})

When I try to send a request, I get an error:

XMLHttpRequest cannot load URL. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.

Answer 1

var dataSet = {
  username: 'username',
  password: 'password',
}

$.ajax({
  type: "GET",
  url: url,
  dataType: 'json',
  crossDomain: true,
  data: dataSet,
  // the origin header has to be set server side
  /* 
  headers: {
   'Access-Control-Allow-Origin': '*'
  },
  */
  success: function(response) {
    console.log(response);
  }
});

parameters have assigned by a dataSet and the option data. the allow origin header has to be set server side, not in the client