'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.

javascripthtmlweb-servicesrest


Solution 1:[1]

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:

  1. A URL or an object representing the request.
  2. 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
}

Solution 2:[2]

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)

Solution 3:[3]

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>

Solution 4:[4]

    $("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);
        }
      });
});

Solution 5:[5]

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();

Solution 6:[6]

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()

Solution 7:[7]

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);
  });

Solution 8:[8]

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.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1
Solution 2
Solution 3 Bhola
Solution 4 aayushi
Solution 5 martinwang1985
Solution 6
Solution 7 Shuvo Amin
Solution 8

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