JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.5.0/fabric.min.js"></script>
<button id="add-text-btn">Add text</button><br><br>
<textarea rows="7" id="add-text-value">Your Text Here</textarea>
<br>
<input id="text-font-size" type="text" class="form-control">
<canvas id='canvas' width="500" height="400" style="border:#000 1px solid;"></canvas>

JavaScript

var canvas = new fabric.Canvas('canvas');
$(document).ready(function() {
$('#text-font-size').keyup(function() {
        var val = $(this).val();
        if (isNaN(val)) {
            alert('please enter number');
            $(this).val('');
        }
        var activeObject = canvas.getActiveObject();
        activeObject.fontSize = val;
        canvas.renderAll();
    });
    $('#add-text-btn').click(function() {
        if ($('#text-font-size').val()) {
            var txtfontsize = $('#text-font-size').val();
        } else {
            var txtfontsize = 40;
        }
        var message = $('#add-text-value').val();
        //var txtfontfamily = $('#font-family').val();
        var new_text = new fabric.IText(message, {
            left: 100,
            top: 100,
            fontSize: txtfontsize,
            //fontFamily: txtfontfamily,
            fill: '#000'
        });
        canvas.add(new_text);
        canvas.setActiveObject(new_text);
    });

    canvas.on('object:selected', function(options) {
        if (options.target) {
            $("textarea#add-text-value").val(options.target.text);
            $("#text-font-size").val(options.target.fontSize);
        }
    });

    canvas.on('object:scaling', function(event) {
        if (event.target) {
            $("textarea#add-text-value").val(event.target.text);
            $("#text-font-size").val(event.target.fontSize);
        }
    });

    canvas.on('object:modified', function(event) {
        if (event.target) {
            event.target.fontSize *= event.target.scaleX;
            event.target.scaleX = 1;
            event.target.scaleY = 1;
            $("textarea#add-text-value").val(event.target.text);
            $("#text-font-size").val(event.target.fontSize);
        }
    });

});