Fetch vs. AjaxCall

The Fetch API has built in methods for different datatypes.
For just regular text/html you’d use the text() method, which returns a promise as well, and chain it with another then call.

fetch('www.testSite').then( x => { 
    return x.text();
}).then( y => {
    console.log(y);
});

The built-ins for the returned content is as follows

• clone() – Creates a clone of a Response object.
• error() – Returns a
  new Response object associated with a network error.
• redirect() – Creates a new response with a different URL.
• arrayBuffer() – Returns a promise that resolves with an ArrayBuffer.
• blob() – Returns a promise that resolves with a Blob.
• formData() – Returns a promise that resolves with a FormData object.
• json() – Returns a promise that resolves with a JSON object.
• text() – Returns a promise that resolves with a USVString (text).

It also allows you to send things to the server, or add your own headers etc.

fetch('www.testSite', {
    method  : 'post',
    headers : new Headers({
        'Content-Type': 'application/x-www-form-urlencoded'
    }),
    body    : new FormData(document.getElementById('myform'))
}).then( response => {
    return response.json(); // server returned valid JSON
}).then( parsed_result => {
    console.log(parsed_result);
});