JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" value="Select cup" onmousedown="selectCup(); return false">
<input type="text" id="test" value="Cup of tea">

JavaScript

function selectCup() {
    var input = document.getElementById("test");
    input.setSelectionRange(0, 3); // Highlights "Cup"
    input.focus();
};