Utility (File): DnD File Parser (CSV,JSON,TXT)

(() => {
	var options = {
		scripts: ["https://d3js.org/d3.v5.min.js"]
	}
const fileToString = (inputFile) => {
	const fr = new FileReader();
	return new Promise((resolve, reject) => {
		fr.onerror = () => {fr.abort(); reject({error:"file reader error"})}
		fr.onload = () => resolve(fr.result); 
		fr.readAsText(inputFile);
})}
const dropHandler = async (e) => {
	e.preventDefault(); //disable default drop behavior
  for await (let file of e.dataTransfer.files) { //loop through dropped files
		let r = {format:file.name.slice(file.name.lastIndexOf(".")+1)}
		const str = await fileToString(file); //convert dropped file to string
		var parse = () => {
			var stringParser = () => {
				var parseStr = (delimiter) => str.split(delimiter);
				var testStr = (delimiter) => str.indexOf(delimiter) > -1
				var t = {hasLines:testStr("\n"),hasComma:testStr(","),hasTab:testStr("\t")};
				return t.hasLines ? parseStr("\n") : t.hasTab ? parseStr("\t") : t.hasComma ? parseStr(",") : [];
			}
			return r.format == "json" ? JSON.parse(str) :
			 r.format == "txt" ? stringParser() :
			 r.format == "csv" ? d3.csvParse(str) : []
		};
		r.name = file.name.replace("."+r.format,""),
		r.data = parse();
		console.log({report:r}); 
		}
 }
window.ondragover = (e) => e.preventDefault(); //Prevent default browser behavior
window.ondrop = (e) => dropHandler(e); //Handle dropped files
const loadScripts = (scripts) => {
	console.log(`Loading External Scripts`);
	var scriptCountdown = scripts.length;
	var loadScript = (url) => {
		var scriptsLoaded = () => {
			scriptCountdown == 0 ? console.log("External scripts loaded. Ready to parse!") : null;
			return true;
		}
		var imported = document.createElement('script');
				imported.src = url;
				imported.addEventListener("load", () => {scriptCountdown--; scriptsLoaded();});
				document.head.appendChild(imported);
	}
	scripts.forEach(loadScript)
}
loadScripts(options.scripts);
})();