JSFiddle - React, Tailwind, and code Playground

HTML

<select id="project">
  <option value="">None</option>
  <option value="33">Some Project</option>
  <option value="32">Best project ever</option>
  <option value="31" selected="selected">Another project</option>
</select>

<select id="person">
  <option data-project_ids="[31, 33]" value="65">John</option>
  <option data-project_ids="[31]" value="66">Liz</option>
  <option data-project_ids="[]" value="67">Jim</option>
</select>

JavaScript

function CheckProjects() {
    var curProject = $('#project').val(); //Get the current select project
    $('#person option').each(function () { //Loop through each option
        var arrProjects = $(this).attr('data-project_ids'); //Put the array of projects in a variable
        if (arrProjects.indexOf(curProject) > -1) { //If current project ID is in array of projects
            $(this).show(); //Show the option
        } else { // Else if current project ID is NOT in array of projects
            $(this).hide(); //hide the option
        }
    });
}

CheckProjects(); //Call the function when we run the page
$('#project').on('change', function() { //When we change the project, call the function
    CheckProjects();
});