JSFiddle - React, Tailwind, and code Playground

HTML

<div class="col-md-3">
    <div class="checkbox checkbox-primary">
        <input type="checkbox" id="fast_dd" onclick="selectElement(this);"></input>
        <label for="fast_dd">Anomalies</label>
    </div>
</div>
<div class="col-md-3">
    <select name="fast" class="selectpicker" disabled>
        <option>Options</option>
    </select>
</div>

JavaScript

function selectElement(object) {
    var parent = object.parentNode;
    var parent_1 = parent.parentNode;
    var child = parent_1.nextElementSibling;
    if (object.checked == true) {
        child.children[0].disabled = false;
    } 
    else {
        child.children[0].disabled = true;
    }
}