create a microsoft outlook add in that allows users to tag an email with a custom field matter id in javascript

To create a Microsoft Outlook Add-in that allows users to tag an email with a custom field Matter ID in JavaScript, follow these steps:

1. Create a new Outlook Add-in project in Visual Studio. Choose "Office Add-ins" -> "Outlook Web Add-in" template and select JavaScript language.

2. In the project, open the Manifest.xml file and add a new Context Menu button with a unique id under the MessageComposeCommandSurface section.

   <ExtensionPoint xsi:type="MessageComposeCommandSurface">
       <OfficeTab id="TabDefault">
           <Group id="msgComposeDemoGroup">
               <Label resid="groupLabel" />
               <!-- Add a control for a menu button. -->
               <Control xsi:type="Menu" id="msgComposeDemoMenu">
                   <Label resid="menuLabel" />
                   <Supertip>
                       <Title resid="menuTitle" />
                       <Description resid="menuToolTip" />
                   </Supertip>
                   <Icon>
                       <bt:Image size="16" resid="icon1_32x32" />
                       <bt:Image size="32" resid="icon1_32x32" />
                       <bt:Image size="80" resid="icon1_32x32" />
                   </Icon>
                   <Items>
                       <Item id="customTag">
                           <Label resid="customTagLabel" />
                           <Supertip>
                               <Title resid="customTagTitle" />
                               <Description resid="customTagToolTip" />
                           </Supertip>
                           <Icon>
                               <bt:Image size="16" resid="icon1_32x32" />
                               <bt:Image size="32" resid="icon1_32x32" />
                               <bt:Image size="80" resid="icon1_32x32" />
                           </Icon>
                       </Item>
                   </Items>
                   <ShowOnMenu>false</ShowOnMenu>
               </Control>
           </Group>
       </OfficeTab>
   </ExtensionPoint>
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3. In the project, open the Home.html file and add a form to define the custom field control with input field for Matter ID.

   <form>
       <div>
           <input type="text" id="matterId" placeholder="Enter Matter ID" />
       </div>
       <br />
       <button id="saveMatterId" class="button">Save</button>
   </form>
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4. In the project, open the Home.js file and add a function to execute when the custom menu button is clicked.

   index.tsx
   function onCustomTagClicked(event) {
       Office.context.mailbox.item.displayNewForm('IPM.Note', {
           customProperties: {
               MatterId: event.target.value
           }
       });
   }
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5. Attach an event listener to the custom menu button to invoke onCustomTagClicked function.

   index.tsx
   function addCustomTagClickListener() {
       var customTagButton = document.getElementById('customTag');
       customTagButton.addEventListener('click', onCustomTagClicked);
   }
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6. In the project, open the App.js file and call the addCustomTagClickListener() function on startup.

   index.tsx
   Office.initialize = function () {
       addCustomTagClickListener();
   };
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That's it! Now the add-in allows users to tag an email with a custom field Matter ID. The Matter ID value is saved as custom property in the email object and can be retrieved and used in other parts of the add-in or integrated with other systems.