function word() {
	switch ( ch ) {
	case 't':
		goNext('t');
		goNext('r');
		goNext('u');
		goNext('e');
		return true;
	case 'f':
		goNext('f');
		goNext('a');
		goNext('l');
		goNext('s');
		goNext('e');
		return false;
	case 'n':
		goNext('n');
		goNext('u');
		goNext('l');
		goNext('l');
		return null;
	case 'N':
		goNext('N');
		goNext('a');
		goNext('N');
		return 'NaN';
	case 'u':
		goNext('u');
		goNext('n');
		goNext('d');
		goNext('e');
		goNext('f');
		goNext('i');
		goNext('n');
		goNext('e');
		goNext('d');
		return void 0;
	default:
		error( 'Unexpected `' + ch + '`' );
	}
}
Matches `true`, `false`, `null`, `undefined`, and `'NaN'`.

## Notes

-   The function parses `NaN` as a string in order for deep equality checks in the main function to pass for `NaN`.

@private
@returns {(boolean|null|string|undefined)} parseed value