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 anew 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);});

Your ajaxCall is returning the responseText from the XMLHttpRequest object. It is filtering it out.

You need to read the response Text in the fetch code.

fetch('/foo/').then(x => x.text()).then(console.log)

You can also use x.json() or x.blob()