wikimedia/mediawiki-extensions-DonationInterface

( function ( $ ) {
    $( function () {
        $( '.emailpreferences-form-col-content-salutation-email-edit-link' ).click( function ( e ) {
                e.preventDefault();
            $( '.emailpreferences-form-col-content-salutation-email-edit-input' ).show();
            $( '.emailpreferences-form-col-content-salutation-email' ).hide();
            $( '.emailpreferences-form-col-content-salutation-email-edit' ).hide();
        } );
        var $submitButton = $( '#save' ),
            $emailField = $( '#email' ),
            isEmailValid = function () {
                var email = $emailField.val().trim(),
                    dotPos = email.lastIndexOf( '.' ),
                    atPos = email.indexOf( '@' ),
                    lastAtPos = email.lastIndexOf( '@' );

                // Needs to be not empty,
                return email !== '' &&
                    // have a '.',
                    dotPos > -1 &&
                    // have (but not start with) an '@',
                    atPos > 0 &&
                    // only have ONE '@'
                    atPos === lastAtPos &&
                    // have at least 1 char between '@' and '.',
                    dotPos > atPos + 1 &&
                    // and not end with a dot
                    dotPos < email.length - 1;
            };

        if ( $emailField.length === 1 ) {
            $submitButton.click( function () {
                if ( !isEmailValid() ) {
                    $emailField.addClass( 'errorHighlight' );
                    return false;
                }
                return true;
            } );

            $emailField.change( function () {
                if ( isEmailValid() ) {
                    $emailField.removeClass( 'errorHighlight' );
                }
            } );
        }

    } );
} )( jQuery );