jQuery UI dialog button text as a variable

This won't work because of the way jQuery handles the button name (can be with or without quotes)

This will work:

var button_name = 'Test';
var dialog_buttons = {}; 
dialog_buttons[button_name] = function(){ closeInstanceForm(Function); }
dialog_buttons['Cancel'] = function(){ $(this).dialog('close'); }   
$('#instanceDialog').dialog({ buttons: dialog_buttons });

What you can do is assign the button in the dialog an ID and then manipulate it using standard jQuery.

$("#dialog_box").dialog({
    autoOpen: false,
    modal: true,
    resizable: false,
    buttons: [{
        text: "Ok",
        "id": "btnOk",
        click: function () {
            //okCallback();
        },

    }, {
        text: "Cancel",
        click: function () {
            //cancelCallback();
        },
    }],
    close: function () {
        //do something
    }
});

Set button text:

 var newLabel = "Updated Label";
 $("#btnOk").html('<span class="ui-button-text">'+ newLabel +'</span>')

The problem here is that the dialog plugin does not assign an id to its buttons, so it's quite difficult to modify them directly.

Instead, initialise the dialog as normal, locate the button by the text it contains and add an id. The button can then be accessed directly to change the text, formatting, enable/disable it, etc.

$("#dialog_box").dialog({
buttons: {
    'ButtonA': function() {
        //... configure the button's function
    }
});
$('.ui-dialog-buttonpane button:contains(ButtonA)').attr("id","dialog_box_send-button");            
$('#dialog_box_send-button').html('Send')       

  1. The button option in jQuery UI dialog accepts objects and arrays.
  2. The buttons are instances of the button widget. Use the API instead of manipulating the buttons yourself.

$(function() {
  // using textbox value instead of variable
  $("#dialog").dialog({
    width: 400,
    buttons: [
      { text: $("#buttonText0").val(), click: function() { $(this).dialog("close"); } }, 
      { text: $("#buttonText1").val(), click: function() { $(this).dialog("close"); } }
    ]
  });
  $("#updateButtonText").on("click", function() {
    var $buttons = $("#dialog").dialog("widget").find(".ui-dialog-buttonpane button");
    console.log($buttons.get());

    $buttons.eq(0).button("option", "label", $("#buttonText0").val());
    $buttons.eq(1).button("option", "label", $("#buttonText1").val());

    // few more things that you can do with button widget
    $buttons.eq(0).button("option", "icons", { primary: "ui-icon-check" });
    $buttons.eq(1).button("disable");

    $("#dialog").dialog("open");
  });
});
@import url("https://code.jquery.com/ui/1.11.4/themes/smoothness/jquery-ui.min.css");
<script src="https://code.jquery.com/jquery-1.11.3.min.js"></script>
<script src="https://code.jquery.com/ui/1.11.4/jquery-ui.min.js"></script>

<div id="dialog" title="Sample Dialog">
  <p>Proceed?</p>
</div>

<p style="text-align: center;">
  <input type="text" id="buttonText0" value="OK">
  <input type="text" id="buttonText1" value="Cancel">
  <input type="button" id="updateButtonText" value="Update Button Text">
</p>