Modal Dialog With Custom Code.

<script type="text/javascript" >
ShowNewFolderModalPopUp();
function ShowNewFolderModalPopUp()
{

var options = SP.UI.$create_DialogOptions();
options.title = "Enter folder name";
options.autosize = true;
options.html =  createFolderDialogElement();
options.showClose= true;
options.allowMaximize = false;
options.dialogReturnValueCallback = FolderNewCallback;
SP.UI.ModalDialog.showModalDialog(options);
}

function createFolderDialogElement() {      
        var dialogElement = jQuery(jQuery('#DialogMarkup').html());
dialogElement.find('#cancelButton').on('click', function() {
        SP.UI.ModalDialog.commonModalDialogClose(SP.UI.DialogResult.cancel, jQuery('#FolderNameTextBox').val());
        });
        dialogElement.find('#SubmitButton').on('click', function() {
        SP.UI.ModalDialog.commonModalDialogClose(SP.UI.DialogResult.OK, jQuery('#FolderNameTextBox').val());
        });      
        return dialogElement.get(0);
    }

function FolderNewCallback(dialogResult, returnValue) {
       
        if(dialogResult == SP.UI.DialogResult.OK && returnValue) {
if(returnValue != '')
{
SP.UI.ModalDialog.RefreshPage(SP.UI.DialogResult.OK);
}
        }
if(dialogResult == SP.UI.DialogResult.cancel) {

        }
    }
</script>

<script type="text/html" id="DialogMarkup">
    <div>
        <label for="FolderNameTextBox">Enter Folder Name :</label>
        <input type="text" id="FolderNameTextBox"/><br><br>
        <input type="button" id="SubmitButton" value="Submit"/>&nbsp; &nbsp;
<input type="button" id="cancelButton" value="Cancel"/>
    </div>
</script>