Before I start, here is the API. Super simple: https://www.cryptonator.com/api
To note, I have worked with api before, but i used a await async function, but for some reason I couldn't get that to work....but I found a tutorial for doing this with XML http request, so I decided to just move forwards doing it in XML because I was able to make a simple Bitcoin ticker.
I am building a simple widget to display the prices of Bitcoin, Litecoin, and Ethereum using the cryptonator API. Like I said above, I made a bitcoin ticker with the first function ( see code below ), and it works great. However, I am having issues trying to get 3 different currencies.
Here is what I am trying to do.
var url = "https://api.cryptonator.com/api/ticker/btc-usd";
xmlhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var json = JSON.parse(this.responseText);
parseJson(json);
}
};
xmlhttp.open("GET", url, true);
xmlhttp.send();
function parseJson(json) {
var usdValue = json["ticker"]["price"];
document.getElementById("data").innerHTML = usdValue;
var usdValue = usdValue.replace(/[^\d.\-]/g, "");
var usd = parseFloat(usdValue);
document.getElementById("data").innerHTML = "$ " + usd.toFixed(2);
}
//
//
var xmlhttp2 = new XMLHttpRequest();
var url2 = "https://api.cryptonator.com/api/ticker/ltc-usd";
xmlhttp2.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var json = JSON.parse(this.responseText);
parseJson(json);
}
};
xmlhttp2.open("GET", url2, true);
xmlhttp2.send();
function parseJson(json) {
var LTCusdValue = json["ticker"]["price"];
// document.getElementById("data2").innerHTML = LTCusdValue;
var LTCusdValue = LTCusdValue.replace(/[^\d.\-]/g, "");
var LTCusd = parseFloat(LTCusdValue);
document.getElementById("data2").innerHTML = "$ " + LTCusd.toFixed(2);
}
//
//
//
var xmlhttp3 = new XMLHttpRequest();
var url3 = "https://api.cryptonator.com/api/ticker/eth-usd";
xmlhttp3.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var json = JSON.parse(this.responseText);
parseJson(json);
}
};
xmlhttp3.open("GET", url3, true);
xmlhttp3.send();
function parseJson(json) {
var ETHusdValue = json["ticker"]["price"];
// document.getElementById("data3").innerHTML = ETHusdValue;
var ETHusdValue = ETHusdValue.replace(/[^\d.\-]/g, "");
var ETHusd = parseFloat(ETHusdValue);
document.getElementById("data3").innerHTML = "$ " + ETHusd.toFixed(2);
}
As you can see, I am trying to make 3 request to 3 different APis, but it isn't working. If I comment out all but one of these functions, it works fine. My issues comes when i try to use all 3 at once. If i use Bitcoin and Litecoin only, it will actually work, but will just break again once I try to use the 3rd function ( to get ethereum price ).
The parseJson function is defined three times. This means that every time you write the function it will overwrite the previous definition. So in your case only the last parseJson function will be used for all three requests. You could do a couple of things.
Write three different variations. (Bad practice)
Though this would be the less favorable of the options. It will require you to have repeated code copied multiple times. This can be done more efficiently.
function parseJson1(json) {
...
}
function parseJson2(json) {
...
}
function parseJson3(json) {
...
}
Add an argument to the function. (Good practice)
Give the parseJson function a second argument that selects the element to output the value. This should be the id of the element you'll want to select.
This is the better solution because it only requires you to write a function once and call it multiple times accounting for the variations.
function parseJson(json, id) {
var output = document.getElementById(id); // Select the element based on the id.
if (output === null) { // If element is not found, stop the function.
return;
}
var price = json["ticker"]["price"];
var usdValue = price.replace(/[^\d.\-]/g, "");
var usd = parseFloat(usdValue);
output.innerHTML = "$ " + usd.toFixed(2);
}
The last technique is applicable to the rest of your code. Be aware of repeating yourself. You'll write much cleaner and better code when you only have to write something once.
If I understood you well you can create a method for all cryptos and avoid repeting the same code. If you run the example below you will be able to see all cryptos and also it's easy to add new ones:
const URL = 'https://api.cryptonator.com/api/ticker/'
const cryptos = ['btc', 'ltc', 'eth']
cryptos.map(crypto => {
fetch(`${URL}${crypto}-usd`)
.then(data => data.json())
.then(({ ticker: { base, price } }) => console.log(`${base}: ${(+price).toFixed(2)}`))
})
We are using fetch that is modern XHR. Hope this help.
You should be able to write an async wrapper function for this using a Promise.. This will allow you to use async/await with XHR..
To make using XHR a lot easier, you can use the built in fetch API.. According to this, most browsers support fetch.. All in all, I prefer using fetch over axios, XHR, etc.. but since you specifically asked about XHR, that is how I answered.
If you did not want to await each response, you can do something like this:
// basic XHR wrapper function for 'get'
function getXHR(url) {
return new Promise(function(resolve, reject) {
const xhr = new XMLHttpRequest();
xhr.open("get", url, true);
xhr.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
this.status == 200
? resolve(this.responseText)
: reject(this.status);
}
};
xhr.send();
});
}
const ethElement = document.getElementById("eth");
const bcElement = document.getElementById("bc");
const lcElement = document.getElementById("lc");
// etherium
getXHR("https://api.cryptonator.com/api/ticker/eth-usd")
.then(eth => {
// Can turn into JSON like this:
//const ethJson = JSON.parse(eth);
ethElement.innerHTML = eth;
})
// bitcoin
getXHR("https://api.cryptonator.com/api/ticker/btc-usd")
.then(bc => {
// Can turn into JSON like this:
//const bcJson = JSON.parse(bc);
bcElement.innerHTML = bc;
})
// litecoin
getXHR("https://api.cryptonator.com/api/ticker/ltc-usd")
.then(lc => {
// Can turn into JSON like this:
//const lcJson = JSON.parse(lc);
lcElement.innerHTML = lc;
})
<h1>eth:</h1>
<pre id="eth"></pre>
<h1>bc:</h1>
<pre id="bc"></pre>
<h1>litecoin:</h1>
<pre id="lc"></pre>
I have created the following demo to show you how to accomplish this using async/await:
Init(); // call 'main' function
// basic XHR wrapper function for 'get'
function getXHR(url) {
return new Promise(function(resolve, reject) {
const xhr = new XMLHttpRequest();
xhr.open("get", url, true);
xhr.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
this.status == 200
? resolve(this.responseText)
: reject(this.status);
}
};
xhr.send();
});
}
// "Main" function
async function Init() {
const ethElement = document.getElementById("eth");
const bcElement = document.getElementById("bc");
const lcElement = document.getElementById("lc");
// etherium
const eth = await getXHR("https://api.cryptonator.com/api/ticker/eth-usd");
const ethJson = JSON.parse(eth);
ethElement.innerHTML = ethJson.ticker.price + " " + ethJson.ticker.target;
// bitcoin
const bc = await getXHR("https://api.cryptonator.com/api/ticker/btc-usd");
const bcJson = JSON.parse(bc);
bcElement.innerHTML = bcJson.ticker.price + " " + bcJson.ticker.target;
// litecoin
const lc = await getXHR("https://api.cryptonator.com/api/ticker/ltc-usd");
const lcJson = JSON.parse(lc);
lcElement.innerHTML = lcJson.ticker.price + " " + lcJson.ticker.target;
}
div h1,
div p {
display: inline;
vertical-align: top;
font-family: 'Open Sans', sans-serif;
line-height: 38px;
}
<div>
<h1>eth:</h1>
<p id="eth"></p>
</div>
<div>
<h1>btc:</h1>
<p id="bc"></p>
</div>
<div>
<h1>ltc:</h1>
<p id="lc"></p>
</div>
Related
I am trying to catch the specific error when a certain API key expires or it reaches its daily response limit(assuming 1000 per day).
const moviesearchEngine=()=>{
let searchBox = document.querySelector('.searchBox');
let movieTitle = document.querySelector('.movieTitle');
let yearofRelease = document.querySelector('.yearofRelease');
let genre = document.querySelector('.genre');
let director = document.querySelector('.director');
let plot = document.querySelector('.plot');
const apiCall = ()=>{
let params = new URLSearchParams({
t:searchBox.value,
apikey:`key`
})
let api = `http://www.omdbapi.com/?${params}`;
//fetching the api orelse showing the error
fetch(api).then((response)=>{
return response.json();
}).then((data)=>{
//assigning the data to variable
console.log(data)
})
}
apiCall();
}
Please Go through your desired API's documention and you would be looking for this sort of information mentioned in the Usage limits section of this api page. If you fail to find anything useful then please contact the support of your desired API.
Then you can proceed like this -
var endpoint = 'http://ip-api.com/json/?fields=status,message,countryCode';
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var response = JSON.parse(this.responseText);
if(response.status !== 'success') {
console.log('query failed: ' + response.message);
return
}
// Redirect
if(response.countryCode == "US") {
window.location.replace("https://google.com/");
}
if(response.countryCode == "CA") {
window.location.replace("https://google.ca/");
}
}
};
xhr.open('GET', endpoint, true);
xhr.send();
Source
I was trying to display an ajax request from a web service in my HTML.
I can display the result in the console but can not retrieve the result and then display it in my HTML.
I want to display the result of the request in "weather-result" div by clicking the "ask-weather" button.
Her is my code.
Thank everyone.
const askWeather = function(result){
var request = new XMLHttpRequest();
request.onreadystatechange = function subFunction() {
if (this.readyState == XMLHttpRequest.DONE && this.status == 200) {
result = JSON.parse(this.responseText);
return result.current_condition.condition;
}
};
request.open("GET", "https://www.prevision-meteo.ch/services/json/paris");
request.send();
}
const ask = document.getElementById('ask-weather');
ask.addEventListener('click', function(){
const weatherResult = document.getElementById('weather-result');
weatherResult.innerHTML = askWeather();
});
<html>
<head>
<link rel="stylesheet" type="text/css" href="base.css">
</head>
<body>
<div><button id="ask-weather">Quelle est la météo sur Paris ?</button></div>
<div id="weather-result"></div>
<script type="text/javascript" src="index.js"></script>
</body>
</html>
This seems like a asynchronous/callback problem here. When the button is clicked, it sends a request somewhere and will return right away (with undefined in case of the code above - this can be checked by saving it in a variable and console.log it).
When askWeather() is called, it could return something itself. The return in request.onreadystatechange cannot return for askWeather as it's happening multiple times and later - after askWeather is done and the request is being sent.
If you pass a function a variable and set it to something new in its body, it will not be changed for the caller. That means doing result = ... does not really help, if you wanted to pass a variabel and get it set by the inner function.
A different approach is necessary to handle this. Here are a few alternatives:
To keep it as most similar to the code you had, you can set the innerHTML in the onreadystatechange function:
const askWeather = function() {
var request = new XMLHttpRequest();
request.onreadystatechange = function subFunction() {
if (this.readyState == XMLHttpRequest.DONE && this.status == 200) {
const result = JSON.parse(this.responseText);
// set it here directly
const weatherResult = document.getElementById('weather-result');
weatherResult.innerHTML = result.current_condition.condition;
}
};
request.open("GET", "https://www.prevision-meteo.ch/services/json/paris");
request.send();
}
const ask = document.getElementById('ask-weather');
ask.addEventListener('click', function() {
askWeather();
});
Make it more general and let askWeather use a callback (call a function when it's "done"):
const askWeather = function(callback) {
var request = new XMLHttpRequest();
request.onreadystatechange = function subFunction() {
if (this.readyState == XMLHttpRequest.DONE && this.status == 200) {
const result = JSON.parse(this.responseText);
// send the result to the passed "callback" function
callback(result.current_condition.condition);
}
};
request.open("GET", "https://www.prevision-meteo.ch/services/json/paris");
request.send();
}
const ask = document.getElementById('ask-weather');
ask.addEventListener('click', function() {
askWeather(function (result) { // this whole function is the "callback" parameter
const weatherResult = document.getElementById('weather-result');
weatherResult.innerHTML = result;
});
});
(a) Let askWeather return a promise and use it in the caller
const askWeather = () => new Promise((resolve, reject) => {
var request = new XMLHttpRequest();
request.onreadystatechange = function subFunction() {
if (this.readyState == XMLHttpRequest.DONE && this.status == 200) {
const result = JSON.parse(this.responseText);
// send the result to the passed "callback" function
resolve(result.current_condition.condition);
}
// not sure about the error path here, but something like this:
if (this.readyState == XMLHttpRequest.DONE && this.status != 200) {
reject(new Error("There was an error with the XMLHttpRequest!"));
}
};
request.open("GET", "https://www.prevision-meteo.ch/services/json/paris");
request.send();
});
const ask = document.getElementById('ask-weather');
ask.addEventListener('click', function() {
askWeather()
.catch((err) => weatherResult.innerHTML = err.message) // to handle possible errors, maybe?
.then((result) => { // like the callback solution, but as promise!
const weatherResult = document.getElementById('weather-result');
weatherResult.innerHTML = result;
});
});
});
(b) Additionally to the Promise solution, in newer browsers there is already async and await syntax:
ask.addEventListener('click', async function() {
try {
const result = await askWeather(); // this "pauses" until the Promise return of `askWeather` resolves (or throws an error if it doesn't)
const weatherResult = document.getElementById('weather-result');
weatherResult.innerHTML = result;
} catch (e) {
// error could be handled here
}
});
Instead of XMLHttpRequest, use the fetch API, which usually should be available if Promises are available in the browsers you support. The solution is in the comments of the original question. With most modern browsers, this should work:
ask.addEventListener('click', async () => {
const response = await fetch("https://www.prevision-meteo.ch/services/json/paris");
const result = await response.json();
const weatherResult = document.getElementById('ask-weather');
weatherResult.innerHTML = result.current_condition.condition;
});
If you don't have to support IE, I would use the fetch alternative.
I hope the other alternatives make it clear, asynchronous patterns can be resolved in JavaScript.
function getJSON(path) {
return new Promise(function(resolve, reject) {
var xhttp = new XMLHttpRequest();
xhttp.open('GET', path, true);
xhttp.onreadystatechange = function() {
if (this.readyState === 4) {
if ((this.status >= 200 && this.status < 300) || this.status === 304) {
var response = JSON.parse(this.responseText);
resolve(response);
} else {
var error = this.statusText;
reject('Http/App Error: ' + error);
}
}
}
xhttp.onerror = processError;
xhttp.onabort = processError;
xhttp.send();
xhttp = null;
function processError(err) {
reject('Network Error: ' + err.target.status);
}
});
}
const ask = document.getElementById('ask-weather')
const weather = document.getElementById('weather-result')
const endpoint = 'https://www.prevision-meteo.ch/services/json/paris'
ask.addEventListener('click', function() {
getJSON(endpoint).then((success) => {
const response = success.current_condition.condition
weather.innerHTML = response
}, (error) => {
console.log(error)
})
})
This is a simple example using Promise. See the fiddle working.
//global variables
var corpArray = new Array(); //store corp classes instances
var corpId = new Array(); //store corp id's
window.onload = init();
function init() {
getNpcCorpId();
console.log(corpId);
getCorpNames(corpId[5]);
}
//get all corporation id's from the game
function getNpcCorpId() {
let conName = new XMLHttpRequest();
conName.onload = function() {
if (this.status == 200) {
let idList = JSON.parse(this.responseText);
idList.forEach(element => {
corpId.push(element);
});
}
};
conName.open(
"get",
"https://esi.evetech.net/latest/corporations/npccorps/?datasource=tranquility",
true
);
conName.send();
}
//get corporation name
function getCorpNames(element) {
console.log(element);
let corpConn = new XMLHttpRequest();
corpConn.onload = () => {
if (this.status == 200) {
console.log(this.responseText);
}
};
corpConn.open(
"get",
`https://esi.evetech.net/latest/corporations/${element}/?datasource=tranquility`,
true
);
corpConn.send();
}
I am trying to create an eve online api, i want to use 2 global varibles to store my retrieved values (because i do not know another way) i will use a couple of functions to use the provieded eve api.I can not acces my corpId individual elements, when i console log all my array ,everything is ok,but when i want to access individual element it appears undefiend.
//global variables
var corpArray = new Array(); //store corp classes instances
var corpId = new Array(); //store corp id's
window.onload = init();
async function init() {
await getNpcCorpId();
console.log(corpId);
getCorpNames(corpId[5]); // asynchronous behaviour - let it be fix using await and async
}
//get all corporation id's from the game
function getNpcCorpId() {
return new Promise(function(resolve, reject) {
let conName = new XMLHttpRequest();
conName.onload = function() {
if (this.status == 200) {
let idList = JSON.parse(this.responseText);
idList.forEach(element => {
corpId.push(element);
});
}
resolve();
};
conName.open(
"get",
"https://esi.evetech.net/latest/corporations/npccorps/?datasource=tranquility",
true
);
conName.send();
});
}
//get corporation name
function getCorpNames(element) {
console.log(element);
let corpConn = new XMLHttpRequest();
corpConn.onload = () => {
if (this.status == 200) {
console.log(this.responseText);
}
};
corpConn.open(
"get",
`https://esi.evetech.net/latest/corporations/${element}/?datasource=tranquility`,
true
);
corpConn.send();
}
This is due to asynchronous behaviour - in simple terms - when you
call getNpcCorpId() it is a http request it will take some time to
execute but next line run immediately so at that point of time corpId
is still blank. So to fix this issue you can use await that will makes
JavaScript wait until the promise returns a result.
Hope this helps you !
I intend to print the USD value of ETH from
"https://api.coinmarketcap.com/v1/ticker/ethereum/"
using JavaScript. However, when I include the script
<script type="text/javascript">
var xmlhttp = new XMLHttpRequest();
var url = "";
xmlhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var json = JSON.parse(this.responseText);
parseJson(json);
}
};
xmlhttp.open("GET", url, true);
xmlhttp.send();
function parseJson(json) {
var time = "<b>Last Updated : " + json["time"]["updated"] + "</b>";
var usdValue = "$" + json["eth"]["price.usd"]["rate"];
document.getElementById("data").innerHTML =
usdValue
}
</script>
in my HTML file, along with other scripts of other Price APIs, the code above returns nothing. What am I doing wrong? I need help please.
Try Something like this
<body>
<div id="data" />
<script type="text/javascript">
var json = new XMLHttpRequest(); // start a new variable to store the JSON in
json.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) { // if HTTP header 200 - ok
var object = JSON.parse(this.responseText); // set the variable 'object' to whatever we get back, in our case it is an array of 10 different arrays
for(var i=0;i<object.length;i++){ // looping through json
var item = object[i];
if(item["symbol"] === "ETH"){ // finding when symbol is ETH
var usdValue = "$" + item["price_usd"]; // Fetching price_usd value
document.getElementById("data").innerHTML = usdValue;
}
}
}
};
json.open(
"GET", // method
"https://api.coinmarketcap.com/v1/ticker/ethereum/", // url
true // async
); // initialise the request
json.send(); //send request
</script>
</body>
Run the code snippet
According https://api.coinmarketcap.com/v1/ticker/ethereum/, the return value of JSON.parse(this.responseText) will be a json array. So pass json[0] to your parseJson().
The parsed json doesn't have field/property of 'time' or 'eth'. I suggest you use following code to get what you want.
let time = `<b>Last Updated : ${new Date(parseInt(json['last_updated'])).toDateString()}</b>`;
let usdValue = `\$${json['price_usd']}`;
I just started with creating custom objects in javascript. I want to set this.someObjVar using code below, but something wrong in my approach. Maybe async response uses it's own scope or thread.
// The code below used like:
someClass = new extfoo.SomeClass();
someClass.loadArrFromFile();
// this will be called far later after async returns
someClass.showSomeObjVar();
extfoo.js
=========
var extfoo = {};
extfoo.SomeClass = function() {
this.someObjVar = [];
this.showSomeObjVar = extfoo.showSomeObjVar;
this.loadArrFromFile = extfoo.loadArrFromFile;
};
// Bad results here
extfoo.showSomeObjVar = function() {
// results '0'
console.log('showSomeObjVar: ' + this.someObjVar.length);
};
// Async array population
extfoo.loadArrFromFile = function() {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
this.someObjVar = xhr.responseText.split('\r\n')
// results '23' elements
console.log("someObjVar length: "+this.someObjVar.length);
}
}
// request code ...
};
Are you certain that this.someObjVar is referencing extfoo?
There's a chance that the this object in the extfoo.loadArrFromFile function is referencing the function itself (xhr.onreadystatechange), and not the extfoo object:
extfoo.loadArrFromFile = function() {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
//I'm going to create a new variable for this function called this.someObjVar
//Cause I don't know about extfoo's.
this.someObjVar = xhr.responseText.split('\r\n')
// results '23' elements
console.log("someObjVar length: "+this.someObjVar.length);
//Whup, end of the line, I guess I'll just forget about that variable I just made.
}
}
// request code ...
};
There are several ways to fix this, but to test, try changing this in the extfoo.loadArrFromFile function to extfoo.
Here's how to fix it:
extfoo.loadArrFromFile = function() {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
//OOOH you mean that object
extfoo.someObjVar = xhr.responseText.split('\r\n')
// results '23' elements
console.log("someObjVar length: "+extfoo.someObjVar.length);
}
}
// request code ...
};
One last thing... is extfoo.SomeClass.someObjVar supposed to be different from extfoo.someObjVar? This code will work if that's the case, but otherwise, you'll want to include a SomeClass in between each reference.
Well since it's an asynchronous request, someClass.loadArrFromFile() will not wait until the request is complete, so someClass.showSomeObjVar() will be called before it's complete.
You could add a termination handler to handle the results:
extfoo.loadArrFromFile = function(done) {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
this.someObjVar = xhr.responseText.split('\r\n')
// results '23' elements
console.log("someObjVar length: "+this.someObjVar.length);
done();
}
}
You could then do something like this:
someClass.loadArrFromFile(function() {
someClass.showSomeObjVar();
});