How to parse json using ajax script in ESP32 app - javascript

I am working on a project using ESP32, I get some data from some sensors and send it to a webpage hosted in the same board.
I read some info on the web and understood that is "better" to send all data from several sensors using json method, so my function to get and send data is this:
void handle_leituras()
{
String results_json = "{ \"data\": " + Data +
"," + "\"hora\": " + Hora +
"," + "\"temp_amb1\": " + Tout + " }";
server.send(200, "application/json", results_json);
}
Testing above function in serial monitor I have this data:
{"data": Domingo, 12/4/2020,"hora": 20:53,"temp_amb1": 25.75}
I found a script that can get only one data and print it on that page, this is the script:
function getData() {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("DATA").innerHTML =
this.responseText;
}
};
xhttp.open("GET", "leituras", true);
xhttp.send();
}
Its my index page code that shows data on webpage:
const char pag_inicial[] PROGMEM = R"=====(
<!DOCTYPE html>
<head><meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0, user-scalable=no\">
<title>My 1st test</title></head>
<html>
<body>
<div id="pagina">
<h1>System XPTO</h1>
<div>
Data: <span id="DATA">ND</span><br>
Hora: <span id="HORA">ND</span><br>
Temperatura Ambiente: <span id="TEMPAMB1">ND</span>
</div>
<div id="botoes">
<button type="button" onclick="sendData(0)" style="width: 80px; height: 30px; margin: 30px;">ON</button>
<button type="button" onclick="sendData(1)" style="width: 80px; height: 30px; margin: 30px;">OFF</button><BR>
</div>
<script>
setInterval(function() {
// Call a function repetatively with 1 Second interval
getData();
}, 1000); //2000mSeconds update rate
//function to set on / off a LED on my board
function sendData(led) {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("LEDState").innerHTML =
this.responseText;
}
};
xhttp.open("GET", "setLED?LEDstate="+led, true);
xhttp.send();
}
function getData() {
var xhttp = new XMLHttpRequest();
xhttp.open("GET", "leituras", true);
xhttp.send();
xhttp.onload = function() {
if (this.status == 200) {
var jsonResponse = JSON.parse(this.responseText);
document.getElementById("DATA").innerHTML = jsonResponse.data;
document.getElementById("HORA").innerHTML = jsonResponse.hora;
document.getElementById("TEMPAMB1").innerHTML = jsonResponse.temp_amb1;
}
else {
console.log(this.status);
}
};
}
</script>
</div>
</body>
</html>
)=====";
My problem is...I don't know how to modify this script to get more sensors values from the described above function.
Anybody can save me please?
Thanks in advance ;)

The standard XMLHttpRequest only supports responseText and responseXML, it does not support responseJSON property. However, as long as your server is sending a valid serialised JSON string, the responseText should contain the JSON code as text, so all you've got to do is to parse it with JSON.parse(), and then you can access each JSON element with dot notation:
function getData() {
var xhttp = new XMLHttpRequest();
xhttp.open("GET", "leituras", true);
xhttp.send();
xhttp.onload = function() {
if (this.status == 200) {
var jsonResponse = JSON.parse(this.responseText);
document.getElementById("DATA").innerHTML = jsonResponse.data;
document.getElementById("HORA").innerHTML = jsonResponse.hora;
document.getElementById("TEMPAMB1").innerHTML = jsonResponse.temp_amb1;
}
else {
console.log(this.status);
}
};
}
This piece of code works for all browsers that supports XMLHttpRequest and JSON as long as the server is sending a valid JSON object.

Related

Parsing JSON Array to print specific elements

Im currently trying to parse JSON data from this api in JS but im not sure how to. As of right now when I press any buttons to give me the data, it prints the arrays out rather than the specific data I want. Ive tried to use the JSON Parse function to retrieve the specific data but it seems its not working. Any help would be greatly appreciated! URL to the API docs: https://www.balldontlie.io/#get-all-players
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var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
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document.getElementById("players").innerHTML =
this.responseText;
}
};
xhttp.open("GET", "https://www.balldontlie.io/api/v1/players", true);
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var xhttp = new XMLHttpRequest();
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var xhttp = new XMLHttpRequest();
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xhttp.open("GET", "https://www.balldontlie.io/api/v1/teams", true);
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<!DOCTYPE html>
<html>
<body style="background-color:peachpuff;" >
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You should parse JSON in xhttp.onreadystatechange, that's a callback when request data success.
For the players data as example, it is an object with data and meta, and the players is in data key which is an Array, so you need to loop inside the array to print the values that you needed.
Here's the example for loadPlayers(). You can apply the same concept to loadGames and loadTeams, please let me know if you still having questions.
function loadPlayers() {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function () {
if (this.readyState == 4 && this.status == 200) {
// parse JSON after response
var players = JSON.parse(this.responseText);
// get 'data' key inside response
var playersData = players.data;
// loop all the players
for (var player of playersData) {
// print last_name to the #players element
document.getElementById("players").innerHTML += "<br />" + player['last_name'];
}
}
};
xhttp.open("GET", "https://www.balldontlie.io/api/v1/players", true);
xhttp.send();
}
In function loadPlayers()
data is an array not object

Serverside send information to vanilla HTML

Is it possible to send information from the serverside to the client side like you would with Pug or EJS but without a view engine?
Right now I am using XHTTP requests to access data but it would be a lot easier to not have to use it so much.
function getAllBears(id){
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("allBear").innerHTML = this.responseText;
}
};
xhttp.open("GET", "allBears", true);
xhttp.send();
}
You can insert a script tag in HTML and stringify the variable you have on server side, then read the serialized global variable on window.
response.body = ('
<html>
<head>
...
</head>
<body>
<p>text...</p>
<script>
window.bar = ###
</script>
</body>
</html>
'.replace(###, JSON.stringify(bar))
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function toJSONSafely (obj: any) {
return JSON.stringify(obj)
.replace(/\u2028/g, '\\u2028')
.replace(/\u2029/g, '\\u2029')
.replace(/<\/script>/g, '<\\/script>')
}
User your javascript inside the html code i.e inline javascript
as shown below
<html>
<head>
</head>
<body>
<p>use this code </p>
<script>
function getAllBears(id){
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("allBear").innerHTML = this.responseText;
}
};
xhttp.open("GET", "allBears", true);
xhttp.send();
}
</script>
</body>
</html>

Javascript i can't add a new paragraph using ajax

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<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<p id="demo2"></p>
<script>
function loadDoc(path, callback) {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
callback(this.responseText);
}
};
xhttp.open("GET", path + "?t=" + Math.random(), true);
xhttp.send();
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document.getElementById("demo2").innerHTML = data ; // do something with data
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function loadDocs() {
loadDoc('/PruebasGeneral/MBVR000008.txt', data1Loaded);
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window.onload = loadDocs;
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You need to have all of that over again. You can't just call open() twice:
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var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
callback(this.responseText);
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};
xhttp.open("GET", path + "?t=" + Math.random(), true);
xhttp.send();
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any solution?
PHP code:
<?php echo $_SERVER['REMOTE_ADDR'];?>
HTML CODE:
<body onload='ip(); ip2();'>
<kbd id='ip' ></kbd>
JavaScript code:
function ip() {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function () {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("ip").innerHTML =
this.responseText;
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};
xhttp.open("POST", "ip.php");
xhttp.send();
}
function ip2() {
setTimeout(function () {
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alert(ip);
}, 1000);
}
First of all you should validate that you are getting the right response from your AJAX request by check that the result is certainly written to the element with id attribute "ip", and than instead of using:
var ip = document.getElementById('ip').value;
You should use Node.textContent to get the text content:
var ip = document.getElementById('ip').textContent;
Code example (without AJAX request):
function ip() {
document.getElementById('ip').innerHTML = '127.0.0.1';
}
function ip2() {
setTimeout(function () {
var ip = document.getElementById('ip').textContent;
console.log(ip);
}, 1000);
}
<body onload="ip(); ip2();">
<kbd id="ip" ></kbd>
You want your Ip Address in java script , so have to put ip address in that tag i think.
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<body onload='ip(); ip2();'>
<kbd id='ip' ><?php echo $ip_address; ?></kbd>
<?php echo $_SERVER['REMOTE_ADDR'];?>
<html>
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run this code you might found what is the problem.

Not able to Json response from rest server

Im trying to parse a Json response from a rest server using JavaScript and display the data.
The rest server works fine its just that i cant parse the data. I have looked at dozens of examples and from my understanding the code looks fine.
This is my first attempt at learning Ajax and if i fix this i can continue with my project.
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{"id":"1","author":"Bill Burke","title":"RESTful Java with JAX-RS","year":"2009"}
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This is the client
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<html>
<head>
<title>Form to create a new resource</title>
<script type="text/javascript">
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var xhr = false;
if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
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try {
xhr = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
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xhr = false;
}
}
}
return xhr;
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function grabFile(file) {
var request = getHTTPObject();
if (request) {
request.onreadystatechange = function() {
parseJ(request);
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request.open("GET", file, true);
request.send(null);
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html console error
html console error after modification
Your server is returning XML, try to force it as JSON and maybe add an accept header to the request from the client.

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