与java中的ajax post调用等效的方法

var xhr = new XMLHttpRequest();
xhr.open("POST", "http://example.com/api", true);
xhr.setRequestHeader("Content-Type", "application/json");
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4 && xhr.status === 200) {
    var response = JSON.parse(xhr.responseText);
    // 处理响应数据
  }
};
var data = {
  key1: "value1",
  key2: "value2"
};
xhr.send(JSON.stringify(data));

var url = "http://example.com/api";
var options = {
  method: "POST",
  headers: {
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    key1: "value1",
    key2: "value2"
  })
};
fetch(url, options)
  .then(function(response) {
    if (response.ok) {
      return response.json();
    } else {
      throw new Error("HTTP error " + response.status);
    }
  })
  .then(function(data) {
    // 处理响应数据
  })
  .catch(function(error) {
    // 处理错误
  });