JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<head>
</head>
<body>
    
    <input type='text' id='tb' />
    <div id='txt'></div>
    
</body>
</html>

JavaScript

$(document).ready(function(){
    $(tb).blur(function(){
        var str  = '';
        var nextFont = 0;
        $.each($(tb).val(),function(i,char){
            if(nextFont == 0){
                if(char == '{'){
                    if($(tb).val().indexOf(i,'}')){
                        str += '<font size="15">';
                        nextFont = $(tb).val().indexOf('}', i);
                    } else {
                        str += char;                    
                    }
                } else {
                   str += char;                
                }
            } else if (nextFont === i) {
                str += '</font>';
                 nextFont = 0;               
            } else {
                str += char; 
            }      
        });
        $("#txt").html(str);
    });
});