How can I add an unremovable prefix to an HTML input field?

Question

Using jQuery, how can I add a default value of http:// into an input field that can’t be removed, but that still allows you to type a URL after it?

Defa

Answer 1

All tested!

$('#myUrl').keyup(function(e) {
  if (this.value.length < 7) {
    this.value = 'http://';
  } else if (this.value.indexOf('http://') !== 0) {
    this.value = 'http://' + String.fromCharCode(e.which);
  }
});

URL: