problem with load of xlsx file

Hi everyone, 

in my project I want to load information from an xls or xlsx file. 

My idea is to: 

1. load xlxs/xls file 

2. convert to json file 

3. use the json 

I tried to setup this piece of code, that is actually running for *.txt or *.json file: 

//\\ ** CARICAMENTO LISTA RICAMBI ** //\\
$scope.app.cad.loadXLSfile=function(fileName){ 
var xmlhttp = new XMLHttpRequest(); //apertura del file sequenze
xmlhttp.onreadystatechange = function() {
	if (this.readyState == 4 && this.status == 200) {
		
 	console.log(">> this: "+ this)
 	listaRicambi = JSON.parse(this.response)
 console.log(listaRicambi) // repair_sequence è il nome dell'oggetto indicato nel file .txt formattato con grammatica json
 	
 } 
};
xmlhttp.open("GET", "app/resources/Uploaded/" + fileName + ".xlsx", true);
xmlhttp.send();
}

So, when I inspect the preview mode console print some error like: 

Uncaught SyntaxError: Unexpected token P in JSON at position 0
 at JSON.parse (<anonymous>)
 at XMLHttpRequest.xmlhttp.onreadystatechange (app.js?v1611219048987:568)

Any idea?

Thank you so much.