如何从前端获取状态码

var xhr = new XMLHttpRequest();
xhr.open('GET', 'http://example.com/api', true);
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4) {
    var statusCode = xhr.status;
    console.log('状态码：', statusCode);
  }
};
xhr.send();

fetch('http://example.com/api')
  .then(function(response) {
    var statusCode = response.status;
    console.log('状态码：', statusCode);
  });

axios.get('http://example.com/api')
  .then(function(response) {
    var statusCode = response.status;
    console.log('状态码：', statusCode);
  });