JSFiddle - React, Tailwind, and code Playground

HTML

<a id="myuniqueid" href='someUrl' title='Bewerken' class='dialog dialog-edit' 
    data-dialogoptions="{&#x22;beforeOpen&#x22;:&#x22;initAlarmZoneForm&#x22;}">
        
    <span class="silk-icon silk-icon-page-edit"></span>
</a>

JavaScript

var tmp = JSON.parse( $("#myuniqueid").attr("data-dialogoptions") );
alert( tmp["beforeOpen"] );