Accessing the contents of a text file is relatively straightforward using an XMLHttpRequest object.
(function(){
var serverRelativeUrlOfMyFile = "/sites/sitecollection/mysite/assets/footer.txt";
var req = new XMLHttpRequest();
req.onreadystatechange=handler;
req.open("GET", serverRelativeUrlOfMyFile, true); // params: (method, url, async)
req.send();
function handler(){
if(req.readyState == 4 && req.status == 200){
// you can now access the file content via the responseText property
document.querySelector("footer").innerHTML = req.responseText;
}
}
})();
The above code is roughly equivalent to the following jQuery:
var serverRelativeUrlOfMyFile = "/sites/sitecollection/mysite/assets/footer.txt";
$.ajax({
url: serverRelativeUrlOfMyFile,
type: "GET"
}).done(handler);
function handler(data){
$("footer").html(data);
}