sheetjs/demos/xhr

XMLHttpRequest and fetch

XMLHttpRequest and fetch browser APIs enable binary data transfer between web browser clients and web servers. Since this library works in web browsers, server conversion work can be offloaded to the client! This demo shows a few common scenarios involving browser APIs and popular wrapper libraries.

Sample Server

The server.js nodejs server serves static files on GET request. On a POST request to /upload, the server processes the body and looks for the file and data fields. It will write the Base64-decoded data from data to the file name specified in file.

To start the demo, run npm start and navigate to http://localhost:7262/

XMLHttpRequest

For downloading data, the arraybuffer response type generates an ArrayBuffer that can be viewed as an Uint8Array and fed to XLSX.read using array type:

/* set up an async GET request */
var req = new XMLHttpRequest();
req.open("GET", url, true);
req.responseType = "arraybuffer";

req.onload = function(e) {
	/* parse the data when it is received */
	var data = new Uint8Array(oReq.response);
	var workbook = XLSX.read(data, {type:"array"});
	/* DO SOMETHING WITH workbook HERE */
};
req.send();

For uploading data, this demo populates a FormData object with string data generated with the base64 output type:

/* generate XLSX as base64 string */
var b64 = XLSX.write(workbook, {bookType:'xlsx', type:'base64'});

/* build FormData with the generated file */
var fd = new FormData();
fd.append('data', b64);

/* send data */
var req = new XMLHttpRequest();
req.open("POST", "/upload", true);
req.send(formdata);

axios and superagent patterns are similar to the XMLHttpRequest pattern but involve much less boilerplate:

/* set up an async GET request with axios */
axios(url, {responseType:'arraybuffer'}).then(function(res) {
	/* parse the data when it is received */
	var data = new Uint8Array(res.data);
	var workbook = XLSX.read(data, {type:"array"});

	/* DO SOMETHING WITH workbook HERE */
});

/* set up an async GET request with superagent */
superagent.get(url).responseType('arraybuffer').end(function(err, res) {
	/* parse the data when it is received */
	var data = new Uint8Array(res.body);
	var workbook = XLSX.read(data, {type:"array"});

	/* DO SOMETHING WITH workbook HERE */
});

fetch

For downloading data, response.blob() resolves to a Blob object that can be converted to ArrayBuffer using a FileReader:

fetch(url).then(function(res) {
	/* get the data as a Blob */
	if(!res.ok) throw new Error("fetch failed");
	return res.blob();
}).then(function(blob) {
	/* configure a FileReader to process the blob */
	var reader = new FileReader();
	reader.addEventListener("loadend", function() {
		/* parse the data when it is received */
		var data = new Uint8Array(this.result);
		var workbook = XLSX.read(data, {type:"array"});

		/* DO SOMETHING WITH workbook HERE */
	});
	reader.readAsArrayBuffer(blob);
});