JSFiddle - React, Tailwind, and code Playground

HTML

<input onchange="userPreviewImage(this)" type="file" accept="image/*" />

JavaScript

window.onload = function () {
    this.userPreviewImage = function (fileInput) {
        var files = fileInput.files;
        var file = files[0];
        var reader = new FileReader();
        reader.onload = function (aImg) {
            $.post("/echo/html/", {
                html: aImg.target.result
            })
            .then(function (data, textStatus, jqxhr) {
                console.log(data, textStatus);
            }, function(jqxhr, textStatus, errorThrown) {
                console.log(textStatus, errorThrown);
            })
        };
        reader.readAsDataURL(file);
    }
}