---
id: 587d7faf367417b2b2512be9
title: JavaScript の XMLHttpRequest メソッドでデータをポストする
challengeType: 6
forumTopicId: 301504
dashedName: post-data-with-the-javascript-xmlhttprequest-method
---

# --description--

以前の例では、外部リソースからデータを受け取りました。 そのリソースが AJAX リクエストをサポートし、あなたが URL を知っていれば、外部リソースにデータを送信することもできます。

JavaScriptの `XMLHttpRequest` メソッドは、データをサーバーにポストするためにも使用されます。 次に例を示します。

```js
const xhr = new XMLHttpRequest();
xhr.open('POST', url, true);
xhr.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
xhr.onreadystatechange = function () {
  if (xhr.readyState === 4 && xhr.status === 201){
    const serverResponse = JSON.parse(xhr.response);
    document.getElementsByClassName('message')[0].textContent = serverResponse.userName + serverResponse.suffix;
  }
};
const body = JSON.stringify({ userName: userName, suffix: ' loves cats!' });
xhr.send(body);
```

これらのメソッドのいくつかは見覚えがあるでしょう。 Here the `open` method initializes the request as a `POST` to the given URL of the external resource, and passes `true` as the third parameter - indicating to perform the operation asynchronously.

The `setRequestHeader` method sets the value of an HTTP request header, which contains information about the sender and the request. It must be called after the `open` method, but before the `send` method. The two parameters are the name of the header and the value to set as the body of that header.

Next, the `onreadystatechange` event listener handles a change in the state of the request. A `readyState` of `4` means the operation is complete, and a `status` of `201` means it was a successful request. Therefore, the document's HTML can be updated.

Finally, the `send` method sends the request with the `body` value. The `body` consists of a `userName` and a `suffix` key.

# --instructions--

Update the code so it makes a `POST` request to the API endpoint. Then type your name in the input field and click `Send Message`. Your AJAX function should replace `Reply from Server will be here.` with data from the server. Format the response to display your name appended with the text `loves cats`.

# --hints--

Your code should create a new `XMLHttpRequest`.

```js
assert(code.match(/new\s+?XMLHttpRequest\(\s*?\)/g));
```

Your code should use the `open` method to initialize a `POST` request to the server.

```js
assert(code.match(/\.open\(\s*?('|")POST\1\s*?,\s*?url\s*?,\s*?true\s*?\)/g));
```

Your code should use the `setRequestHeader` method.

```js
assert(
  code.match(
    /\.setRequestHeader\(\s*?('|")Content-Type\1\s*?,\s*?('|")application\/json;\s*charset=UTF-8\2\s*?\)/g
  )
);
```

Your code should have an `onreadystatechange` event handler set to a function.

```js
assert(code.match(/\.onreadystatechange\s*?=/g));
```

Your code should get the element with class `message` and change its `textContent` to `userName loves cats`

```js
assert(
  code.match(
    /document\.getElementsByClassName\(\s*?('|")message\1\s*?\)\[0\]\.textContent\s*?=\s*?.+?\.userName\s*?\+\s*?.+?\.suffix/g
  )
);
```

Your code should use the `send` method.

```js
assert(code.match(/\.send\(\s*?body\s*?\)/g));
```

# --seed--

## --seed-contents--

```html
<script>
  document.addEventListener('DOMContentLoaded', function(){
    document.getElementById('sendMessage').onclick = function(){

      const userName = document.getElementById('name').value;
      const url = 'https://jsonplaceholder.typicode.com/posts';
      // Add your code below this line


      // Add your code above this line
    };
  });
</script>

<style>
  body {
    text-align: center;
    font-family: "Helvetica", sans-serif;
  }
  h1 {
    font-size: 2em;
    font-weight: bold;
  }
  .box {
    border-radius: 5px;
    background-color: #eee;
    padding: 20px 5px;
  }
  button {
    color: white;
    background-color: #4791d0;
    border-radius: 5px;
    border: 1px solid #4791d0;
    padding: 5px 10px 8px 10px;
  }
  button:hover {
    background-color: #0F5897;
    border: 1px solid #0F5897;
  }
</style>

<h1>Cat Friends</h1>
<p class="message box">
  Reply from Server will be here
</p>
<p>
  <label for="name">Your name:
    <input type="text" id="name"/>
  </label>
  <button id="sendMessage">
    Send Message
  </button>
</p>
```

# --solutions--

```html
<script>
  document.addEventListener('DOMContentLoaded', function(){
    document.getElementById('sendMessage').onclick = function(){

      const userName = document.getElementById('name').value;
      const url = 'https://jsonplaceholder.typicode.com/posts';
      // Add your code below this line
      const xhr = new XMLHttpRequest();
      xhr.open('POST', url, true);
      xhr.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
      xhr.onreadystatechange = function () {
        if (xhr.readyState === 4 && xhr.status === 201){
          const serverResponse = JSON.parse(xhr.response);
          document.getElementsByClassName('message')[0].textContent = serverResponse.userName + serverResponse.suffix;
       }
     };
     const body = JSON.stringify({ userName: userName, suffix: ' loves cats!' });
     xhr.send(body);
      // Add your code above this line
    };
  });
</script>

<style>
  body {
    text-align: center;
    font-family: "Helvetica", sans-serif;
  }
  h1 {
    font-size: 2em;
    font-weight: bold;
  }
  .box {
    border-radius: 5px;
    background-color: #eee;
    padding: 20px 5px;
  }
  button {
    color: white;
    background-color: #4791d0;
    border-radius: 5px;
    border: 1px solid #4791d0;
    padding: 5px 10px 8px 10px;
  }
  button:hover {
    background-color: #0F5897;
    border: 1px solid #0F5897;
  }
</style>

<h1>Cat Friends</h1>
<p class="message">
  Reply from Server will be here
</p>
<p>
  <label for="name">Your name:
    <input type="text" id="name"/>
  </label>
  <button id="sendMessage">
    Send Message
  </button>
</p>
```
