how to send post in javascript code example

Example 1: http request javascript

function httpGetAsync(url, callback) {
  var xmlHttp = new XMLHttpRequest();
  xmlHttp.onreadystatechange = function() { 
    if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
      callback(xmlHttp.responseText);
  }
  xmlHttp.open("GET", url, true); // true for asynchronous 
  xmlHttp.send(null);
}

Example 2: post method javascript code

const postData = async ( url = '', data = {})=>{
    console.log(data);
      const response = await fetch(url, {
      method: 'POST', 
      credentials: 'same-origin',
      headers: {
          'Content-Type': 'application/json',
      },
     // Body data type must match "Content-Type" header        
      body: JSON.stringify(data), 
    });

      try {
        const newData = await response.json();
        console.log(newData);
        return newData;
      }catch(error) {
      console.log("error", error);
      }
  }