Office Samples

link - learn.microsoft.com/en-us/office/dev/add-ins/overview/create-an-office-add-in-from-script-lab 

You may come across code samples that use JQuery.
You may see code samples that contain JQuery in Script Lab.

npm install jquery --save 
npm install @types/jquery --save-dev 

<script src="https://ajax.aspnetcdn.com/ajax/jquery/jquery-3.3.1.js"></script> 

( function () { 
   Office.initialize = function (reason) { 
      $(document).ready(function) () { 
         $('body').html('display some text'); 
      }); 
   }; 
}) (); 

Home.html

  <button class="Button Button--primary" id="shadecell-button"> 
     <span class="Button-icon"><i class="ms-Icon ms-Icon--plus"></i></span> 
     <span class="Button-label" id="button-text"></span> 
  </button> 

Home.js

Office.initialize = function (reason) { 
    $(document).ready(function () { 

       $('#button-text').text("Shade Cell");  

       $('#shadecell-button').click(shadeCell);  
    }); 
}; 

function shadeCell() { 
    Excel.run(function (ctx) { 
        var _range = ctx.workbook.worksheets.getItem("Sheet1").getRange("A1"); 

        return ctx.sync() 
            .then(function () { 
                _range.format.fill.color = "orange"; 
            }) 

            .then(ctx.sync); 
    }) 
    .catch(errorHandler); 
}