JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" />

JavaScript

$(document).ready(function() {
    $('input').on('keyup', function() {
        if (this.value[0] != this.value[0].toUpperCase()) {
            // store current positions in variables
            var start = this.selectionStart;
            var end = this.selectionEnd; 
            this.value = this.value[0].toUpperCase() + this.value.substring(1);
            // restore from variables...
            this.setSelectionRange(start, end);
        }
    });
});