How to convert onload client script into widget

[Donabelle]

Hello team, I want to move/convert my onload client script to widget since DOM Manipulation is not a best practice to use in client script. I want to hide the buttons and icons in my MRVS, this script is working but not advisable to use in client script. Can someone help me convert this into widget?

      // for (i = 0; i < btn.length; i++) {

                //     if (btn[i].innerText == 'Add') {

                //         // btn[i].disabled="disabled";

                //         //If you want to hide it fully, then use below line.

                //         btn[i].style.display = 'None';

                //     }

                // }

                // var btn = this.document.getElementsByClassName("btn btn-default");

                // for (i = 0; i < btn.length; i++) {

                //     if (btn[i].innerText == 'Remove All') {

                //         // btn[i].disabled="disabled";

                //         //If you want to hide it fully, then use below line.

                //         btn[i].style.display = 'None';

                //     }

                // }

   // var sheets = this.document.styleSheets;

    // var sheet = sheets[0];

    // //This hides the row-level buttons

    // sheet.insertRule('a.fa-close { display: none !important; }');

    // var sheets = this.document.styleSheets;

    // var sheet = sheets[0];

    // //This hides the row-level buttons

    // sheet.insertRule('a.fa-pencil { display: none !important; }');