JSFiddle - React, Tailwind, and code Playground

HTML

<textarea></textarea>
<button>convert</button>

JavaScript

var map = {
    ':)':   '<img src="/images/happy.jpg"/>',
    ';(':   '<img src="/images/wink.jpg"/>'
};


document.getElementsByTagName('button')[0].addEventListener('click', function()  {
    var text    = document.getElementsByTagName('textarea')[0].value;
    
    
    Object.keys( map ).forEach(function( ico ) {
        // escape special characters for regex
        var icoE   = ico.replace(/([.?*+^$[\]\\(){}|-])/g, "\\$1");

        // now replace actual symbols
        text  = text.replace( new RegExp(icoE, 'g'), map[ico] );
    });
    
    alert(text);
}, false);