JSFiddle - React, Tailwind, and code Playground

HTML

<select id="supplier">
    <option value="1">1</option>
    <option value="2">2</option>
</select>

JavaScript

function addOptions(input) {
    var sel = document.getElementById("supplier");
    if (typeof input === "string") {
        input = [input];
    }
    sel.options.length = 0;  // Clears all current options
    for (var i = 0; i < input.length; i++) {
        sel.options[sel.options.length] = new Option(input[i], input[i]);
        // This APPENDS options
    }
}

addOptions("fff");