Gets and sets the username portion of the URL.

const myURL = new URL('https://abc:xyz@example.com');
console.log(myURL.username);
// Prints abc

myURL.username = '123';
console.log(myURL.href);
// Prints https://123:xyz@example.com/

Any invalid URL characters appearing in the value assigned the username property will be percent-encoded. The selection of which characters to percent-encode may vary somewhat from what the parse and format methods would produce.