Question

Basically, I wrote this code:

var paramStr = '';
for (var n in params) {
    paramStr += '&' + n + '=' + params[n];
}
xhr.open(method, url + '?' + paramStr);

Do I need to remove the first ampersand or can I leave it as is with no side effects?

Answer 1

You can leave it as is.

www.something.com?&something=something_else is a valid url

But what I would do so it looks right is add a dummy param:

var paramStr = '?dummy'; //or any other value
for (var n in params) {
    paramStr += '&' + n + '=' + params[n];
}
xhr.open(method, url + paramStr);

or @slobodan‘s solution:

var paramStr = '?'; 
for (var n in params) {
    paramStr += n + '=' + params[n] + '&'; 
    // because you can have a `&` at the end
}
xhr.open(method, url + paramStr);