Accessing JSON from last.fm API - javascript

I'm very new to JavaScript and have been looking for a solution for a while with no success. I'm trying to use the Last.fm API to retrieve the currently playing track on my account. This is what I have so far:
<html>
<body>
<p>this is an experiment!</p>
<script type="text/javascript">
const request = new XMLHttpRequest();
request.open('GET', 'http://ws.audioscrobbler.com/2.0/?method=user.getrecenttracks&user='+[MY_USERNAME]+'&api_key='+[MY_API_KEY]+'&format=json');
request.send();
request.onload = () => {
if (request.status === 200) {
console.log("Success");
var song = JSON.parse(request.response).recenttracks.track[0].name;
console.log(song);
}
};
request.onerror = () => {
console.log("error")
};
</script>
</body>
</html>
and I get an error in the console when I open the file in my browser. Any help is appreciated :)
Update: everything worked when I gave it the direct URL, e.g. I took out the +s and put the API key directly in.

I checked your code with the test-account and it works fine. So probably you get the empty result, let's add some checks:
request.onload = () => {
if (request.status === 200) {
// look at the response
console.log(request.response);
const recenttracks = JSON.parse(request.response).recenttracks;
if (!recenttracks.track || !recenttracks.track.length) {
console.log('track is empty');
return;
}
const song = recenttracks.track[0].name;
console.log(song);
}
};

It looks like you should use onreadystatechange to catch the response instead of onload.
Example:
request.onreadystatechange = function() {
if (this.status == 200) {
console.log(this.responseText);
}
};
You can read more about XMLHttp Requests here:
https://www.w3schools.com/xml/ajax_xmlhttprequest_send.asp

Related

Data not displaying in JavaScript API

I am making a Pokedex API as a side project and I can not display the data needed to display in the different text boxes. I am using a GET request to request the height, weight, type, and ability.
<script>
$("button").click( function(){
var pokemonName = $('pokemon').val(pokemon);
event.preventDefault();
getPokemonData(pokemonName);
})
function getPokemonData(pokemonName){
var request = new XMLHttpRequest()
//GET request with link
request.open('GET','https://pokeapi.co/api/v2/pokemon/' + pokemonName, true);
// request for data
request.onload =function(){
var data = JSON.parse(this.response)
if(request.status >= 200 && request.status <= 400)
{
// outputs data
$(pokemonheight).val(response.height)
$(pokemonweight).val(response.weight)
$(pokemonAblity).val(response.ability)
$(pokemonType).val(response.type)
}
else
{
alert ("Error");
}
request.send();
}
}
</script>
</html>
I have tried setting a variable that would be equal to the response JSON element and then input that into the value of the textbox.
I do not have anything returned as expected or input displayed in the console if declared.
Issue(s)
There were a few issues with your code:
var pokemonName = $('pokemon').val(pokemon); you are setting the value of some element named pokemon (not valid) here
var data = JSON.parse(this.response); where is this.response being set? Shouldn't we be receiving response in the callback?
request.send(); is inside of the onload event, so the request never gets sent
Critiques
My main critique here is that you included a fairly large library (jQuery), and didn't utilize it to make the request. $.ajax is well documented and cleans up a lot of the intricacies of XMLHttpRequest.
The solution
$("button").click(function() {
var pokemonName = $('#pokemon').val();
//event.preventDefault();
getPokemonData(pokemonName);
})
function getPokemonData(pokemonName) {
var request = new XMLHttpRequest()
//GET request with link
request.open('GET', 'https://pokeapi.co/api/v2/pokemon/' + pokemonName, true);
// request for data
request.onload = function(response) {
var data = JSON.parse(response.currentTarget.response)
if (request.status >= 200 && request.status <= 400) {
// outputs data
console.log(data)
} else {
alert("Error");
}
}
request.send();
}
<input id="pokemon" value="12" />
<button>search</button>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
Taking all the above issues into account, I was able to get a working example of what it should ultimately look like.
Hope this helps!

How to call a REST web service API from JavaScript?

I have an HTML page with a button on it. When I click on that button, I need to call a REST Web Service API. I tried searching online everywhere. No clue whatsoever. Can someone give me a lead/Headstart on this? Very much appreciated.
I'm surprised nobody has mentioned the new Fetch API, supported by all browsers except IE11 at the time of writing. It simplifies the XMLHttpRequest syntax you see in many of the other examples.
The API includes a lot more, but start with the fetch() method. It takes two arguments:
A URL or an object representing the request.
Optional init object containing the method, headers, body etc.
Simple GET:
const userAction = async () => {
const response = await fetch('http://example.com/movies.json');
const myJson = await response.json(); //extract JSON from the http response
// do something with myJson
}
Recreating the previous top answer, a POST:
const userAction = async () => {
const response = await fetch('http://example.com/movies.json', {
method: 'POST',
body: myBody, // string or object
headers: {
'Content-Type': 'application/json'
}
});
const myJson = await response.json(); //extract JSON from the http response
// do something with myJson
}
Your Javascript:
function UserAction() {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
alert(this.responseText);
}
};
xhttp.open("POST", "Your Rest URL Here", true);
xhttp.setRequestHeader("Content-type", "application/json");
xhttp.send("Your JSON Data Here");
}
Your Button action::
<button type="submit" onclick="UserAction()">Search</button>
For more info go through the following link (Updated 2017/01/11)
Here is another Javascript REST API Call with authentication using json:
<script type="text/javascript" language="javascript">
function send()
{
var urlvariable;
urlvariable = "text";
var ItemJSON;
ItemJSON = '[ { "Id": 1, "ProductID": "1", "Quantity": 1, }, { "Id": 1, "ProductID": "2", "Quantity": 2, }]';
URL = "https://testrestapi.com/additems?var=" + urlvariable; //Your URL
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = callbackFunction(xmlhttp);
xmlhttp.open("POST", URL, false);
xmlhttp.setRequestHeader("Content-Type", "application/json");
xmlhttp.setRequestHeader('Authorization', 'Basic ' + window.btoa('apiusername:apiuserpassword')); //in prod, you should encrypt user name and password and provide encrypted keys here instead
xmlhttp.onreadystatechange = callbackFunction(xmlhttp);
xmlhttp.send(ItemJSON);
alert(xmlhttp.responseText);
document.getElementById("div").innerHTML = xmlhttp.statusText + ":" + xmlhttp.status + "<BR><textarea rows='100' cols='100'>" + xmlhttp.responseText + "</textarea>";
}
function callbackFunction(xmlhttp)
{
//alert(xmlhttp.responseXML);
}
</script>
<html>
<body id='bod'><button type="submit" onclick="javascript:send()">call</button>
<div id='div'>
</div></body>
</html>
$("button").on("click",function(){
//console.log("hii");
$.ajax({
headers:{
"key":"your key",
"Accept":"application/json",//depends on your api
"Content-type":"application/x-www-form-urlencoded"//depends on your api
}, url:"url you need",
success:function(response){
var r=JSON.parse(response);
$("#main").html(r.base);
}
});
});
I think add if (this.readyState == 4 && this.status == 200) to wait is better:
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
// Typical action to be performed when the document is ready:
var response = xhttp.responseText;
console.log("ok"+response);
}
};
xhttp.open("GET", "your url", true);
xhttp.send();
If that helps anyone, if you are ok with an external library then I can vouch for Axios, which has a pretty clean API and rich documentation to deal with REST calls, here's an example below:-
const axios = require('axios');
axios.get('/user?ID=12345')
.then(function (response) {
// handle success
console.log(response);
});
Before we try to put anything on the front end of the website, let's open a connection the API. We'll do so using XMLHttpRequest objects, which is a way to open files and make an HTTP request.
We'll create a request variable and assign a new XMLHttpRequest object to it. Then we'll open a new connection with the open() method - in the arguments we'll specify the type of request as GET as well as the URL of the API endpoint. The request completes and we can access the data inside the onload function. When we're done, we'll send the request.
// Create a request variable and assign a new XMLHttpRequest object to it.
var request = new XMLHttpRequest()
// Open a new connection, using the GET request on the URL endpoint
request.open('GET', 'https://ghibliapi.herokuapp.com/films', true)
request.onload = function () {
// Begin accessing JSON data here
}
}
// Send request
request.send()
By far, the easiest for me is Axios. You can download the node module or use the CDN for your simpler projects.
CDN:
<script src="https://cdn.jsdelivr.net/npm/axios/dist/axios.min.js"></script>
Code example for GET/POST:
let postData ={key: "some value"}
axios.get(url).then(response =>{
//Do stuff with the response.
})
axios.post(url, postData).then(response=>{
//Do stuff with the response.
});
Without a doubt, the simplest method uses an invisible FORM element in HTML specifying the desired REST method. Then the arguments can be inserted into input type=hidden value fields using JavaScript and the form can be submitted from the button click event listener or onclick event using one line of JavaScript. Here is an example that assumes the REST API is in file REST.php:
<body>
<h2>REST-test</h2>
<input type=button onclick="document.getElementById('a').submit();"
value="Do It">
<form id=a action="REST.php" method=post>
<input type=hidden name="arg" value="val">
</form>
</body>
Note that this example will replace the page with the output from page REST.php.
I'm not sure how to modify this if you wish the API to be called with no visible effect on the current page. But it's certainly simple.
Usual way is to go with PHP and ajax. But for your requirement, below will work fine.
<body>
https://www.google.com/controller/Add/2/2<br>
https://www.google.com/controller/Sub/5/2<br>
https://www.google.com/controller/Multi/3/2<br><br>
<input type="text" id="url" placeholder="RESTful URL" />
<input type="button" id="sub" value="Answer" />
<p>
<div id="display"></div>
</body>
<script type="text/javascript">
document.getElementById('sub').onclick = function(){
var url = document.getElementById('url').value;
var controller = null;
var method = null;
var parm = [];
//validating URLs
function URLValidation(url){
if (url.indexOf("http://") == 0 || url.indexOf("https://") == 0) {
var x = url.split('/');
controller = x[3];
method = x[4];
parm[0] = x[5];
parm[1] = x[6];
}
}
//Calculations
function Add(a,b){
return Number(a)+ Number(b);
}
function Sub(a,b){
return Number(a)/Number(b);
}
function Multi(a,b){
return Number(a)*Number(b);
}
//JSON Response
function ResponseRequest(status,res){
var res = {status: status, response: res};
document.getElementById('display').innerHTML = JSON.stringify(res);
}
//Process
function ProcessRequest(){
if(method=="Add"){
ResponseRequest("200",Add(parm[0],parm[1]));
}else if(method=="Sub"){
ResponseRequest("200",Sub(parm[0],parm[1]));
}else if(method=="Multi"){
ResponseRequest("200",Multi(parm[0],parm[1]));
}else {
ResponseRequest("404","Not Found");
}
}
URLValidation(url);
ProcessRequest();
};
</script>

Pinterest pins through HTML/JavaScript

I Have been using pins to get the information of a pin from pinterest.
The following is the script being used:
<script type="text/javascript">
function getresponse1()
{
var xmlHttp = new XMLHttpRequest();
xmlHttp.open( "GET", "https://widgets.pinterest.com/v3/pidgets/pins/info/?pin_ids="+{Pin ID});
alert(xmlHttp.status);
var data=xmlHttp.responseText;
var jsonResponse = JSON.parse(data);
var pin_url="www.pinterest.com/pin/"+pin_id+"/";
var page_name=(jsonResponse["data"][0].pinner.full_name);
alert(page_name);
}
</script>
Whenever XMLHttpRequest() method is being invoked the status returned is always 0 and the xmlHttp.responseText is empty.
But when the link is opened in a browser the response is correct and has all the information of the pin.
EDIT:
Tried implementing cross domain too. But yet the status returns 0.
New Script:
<script type="text/javascript">
function getresponse1()
{
var xhr = new XMLHttpRequest();
var url="https://widgets.pinterest.com/v3/pidgets/pins/info/?pin_ids=308074430730714588";
if ("withCredentials" in xhr) {
xhr.open("GET", url, true);
} else if (typeof XDomainRequest != "undefined") {
xhr = new XDomainRequest();
xhr.open(method, url);
} else {
xhr = null;
}
alert(xhr.status);
var data=xhr.responseText;
}
</script>
Please let me know where i'm making mistake. Thanks in advance
Note: I'm using Chrome browser
This is an general issue, as you try to do an ajax request to a different site (cross domain).
This isn't an new issue at all, I think here it is well explained and this posts provide also some thoughts about possible solutions.
AJAX is asynchronous, so your data will only be available from some kind of callback.
xhr.onload = function() {
if (xhr.status >= 200 && xhr.status < 400) {
var data = JSON.parse(request.responseText);
}
};

ReferenceError: CSV is not defined

I am using the jquery.csv-0.71.min.js lib to load a csv file and convert it to an array. However, when loading my webpage:
<script src="assets/lib/jquery/dist/jquery.min.js"></script>
<script src="assets/lib/bootstrap/dist/js/bootstrap.min.js"></script>
<!-- Jquery-csv -->
<script src="assets/js/jquery.csv-0.71.min.js"></script>
<script>
(function() {
var data;
var url = 'data/data.csv';
function makeRequest(url) {
var xhr = new XMLHttpRequest();
xhr.open('GET', url);
xhr.onload = function() {
if (xhr.readyState === 4 && xhr.status === 200) {/*run code*/}
};
xhr.send(null);
}
})();
data = CSV.toArrays(xhr.responseText);
console.log(data);
</script>
I get in the console:
ReferenceError: CSV is not defined at 'data = CSV.toArrays(xhr.responseText);'
Any recommendations what I am doing wrong?
I appreciate your replies!
UPDATE
I put my code into the document read funciton, however, I still get the same error as above.
$(document).ready(function() {
(function() {
var data;
var url = 'data/data.csv';
function makeRequest(url) {
var xhr = new XMLHttpRequest();
xhr.open('GET', url);
xhr.onload = function() {
if (xhr.readyState === 4 && xhr.status === 200) {/*run code*/
}
};
xhr.send(null);
}
})();
data = CSV.toArrays(xhr.responseText);
console.log(data);
});
You code is executed before browser loads the CSV script.
Wrap you JavaScript code with
$( document ).ready(function() {
// PUT YOUR JavaScript CODE HERE
});
This will make browser to wait, until all your scripts are loaded, and only after to execute the code.
You can check the documentation of the jquery csv here. It says that you should invoke methods like this:
$.csv.toArrays(csv);

XMLHttpRequest.responseText doesnt write the value when calling a URL

There may be a small error in my code. please advice me.
I want to call a URL and display the value in div on pageload.I wrote this code from SO but the responseText doesnt write the value in the div element's innerhtml
Code
<script type="text/javascript" >
var req ;
// Browser compatibility check
if (window.XMLHttpRequest) {
req = new XMLHttpRequest();
} else if (window.ActiveXObject) {
try {
req = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
req = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {}
}
}
var req = new XMLHttpRequest();
req.open("GET", "www.example.com/Default.aspx?usrname=john",true);
req.onreadystatechange = function () {
document.getElementById('divTxt').innerHTML = "My Status: " + req.responseText;
}
req.send(null);
</script>
<html>
<head/>
<body>
<div id="divTxt"></div></body>
</html>
The output I get is
My status :
PS: I want this to be done after pageload and The url returns a value "online" when called manually
EDIT
This is the code I referred : code
You cannot ajax a url from another domain unless it has implemented CORS
If you need to get data from somewhere which is not same origin you need to use JSONP
Also to debug, try calling the url from the locationbar to see if you receive valid data for your request
req.onreadystatechange = function () {
document.getElementById('divTxt').innerHTML = "My Status: " + req.responseText;
}
you have to check, if the request was successful:
if (req.readyState === 4) {
// what should be done with the result
}
finally, it has to look like this:
req.onreadystatechange = function () {
if (req.readyState === 4) {
document.getElementById('divTxt').innerHTML = "My Status: " + req.responseText;
}
}

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