How can I add autocomplete="off" to a form field?

$fields->push( new TextField( "Your Phone") );

Afaik the only way to do that is extending the (Text)Field. Something like

class MyAutocompleteTextField extends TextField { 

	function Field() {
		$attributes = array(
			'type' => 'text',
			'class' => 'text' . ($this->extraClass() ? $this->extraClass() : ''),
			'id' => $this->id(),
			'name' => $this->Name(),
			'value' => $this->Value(),
			'tabindex' => $this->getTabIndex(),
			'maxlength' => ($this->maxLength) ? $this->maxLength : null,
			'size' => ($this->maxLength) ? min( $this->maxLength, 30 ) : null
		);

		if($this->disabled) $attributes['disabled'] = 'disabled';

		// add the new attribute here:              <==========
		$attributes['autocomplete'] = 'off';

		return $this->createTag('input', $attributes);
	}

}

Then

$fields->push( new MyAutocompleteTextField( "Your Phone") );

On a similar topic, what's the best way to add autocomplete = "off" to the password field on the Login page?

Or all password fields for that matter.

I don't want to hack the core.

This is how I've done it, not the greatest but works...

_config.php

Object::useCustomClass('MemberLoginForm','CustomLoginForm');

CustomLoginForm.php

class CustomLoginForm extends MemberLoginForm {
	public function __construct($controller, $name, $fields = null, $actions = null, $checkCurrentUser = true) {
		parent::__construct($controller, $name, $fields, $actions);
		Requirements::customScript(<<<JS
			jQuery(document).ready(function(){
				jQuery('#CustomLoginForm_LoginForm_Password').attr('autocomplete','off');
			});
JS
);
	}
}