Javascript Sending form data using iframe

Javascript-FileUploader.js

"use strict";

document.getElementById("file-upload-form").addEventListener("submit", (e) => {
    e.preventDefault();


    this.inputElement = [];
    this.iframeName = "uploader-facade";
    this.form = document.createElement("form");
    this.iframe = document.createElement("iframe");
    this.iframeElement = document.getElementById(this.iframeName);
    this.formAttributes = {
        target: this.iframeName,
        action: "upload.php",
        method: "POST",
        enctype: "multipart/form-data"
    };


    // Let's append the iFrame used to send our data
    this.iframe.name = this.iframeName;
    this.iframe.id = this.iframeName;
    this.iframe.style.display = "block";// change to none to hide iframe

    if (this.iframeElement)
        document.body.removeChild(this.iframeElement);
    
    document.body.appendChild(this.iframe);

    
    //  fire when iframe finish load
    let onLoad = (e) => {
        var iframeDocument = e.target.contentDocument || e.target.contentWindow.document;
        console.log("Json Document: ", JSON.parse(iframeDocument.body.innerHTML));
    };

    // Add load listener to iframe
    this.iframe.addEventListener("load", onLoad);


    // target all form input elements of type file from the event,
    for (let i = 0; i < e.target.elements.length; i++) {
        if (e.target.elements[i].nodeName === "INPUT" && e.target.elements[i].type === "file") {
            this.inputElement[i] = e.target.elements[i].cloneNode(true);
            this.inputElement[i].files = e.target.elements[i].files;
            this.form.appendChild(this.inputElement[i]);
        }
    }

    // Set form all attributes
    for (let attribute in this.formAttributes) {
        if (this.formAttributes.hasOwnProperty(attribute))
            this.form.setAttribute(attribute, this.formAttributes[attribute]);
    }

    // Submit form
    this.form.submit();

    return this;
});