JAVASCRIPT

add a trailing slash javascript url

// Add trailing slash even when a query is present.
// supported in all modern browsers
let url = new URL("a?foo=bar", "https://example.com");

if (url.pathname[url.pathname.length - 1] != "/") {
	url.pathname += "/";
}

// https://example.com/a/?foo=bar
console.log(url.toString());

js add trailing slash to url (if not present)

var lastChar = url.substr(-1); // Selects the last character
if (lastChar != '/') {         // If the last character is not a slash
   url = url + '/';            // Append a slash to it.
}

// The temporary variable name can be omitted, and directly embedded in the assertion:

if (url.substr(-1) != '/') url += '/';

// Since the goal is changing the url with a one-liner, the following solution can also be used:

url = url.replace(//?$/, '/');
// If the trailing slash exists, it is replaced with /.
// If the trailing slash does not exist, a / is appended to the end (to be exact: The trailing anchor is replaced with /).