Update httpPost.md

snippets/httpPost.md

@@ -2,29 +2,38 @@
 
 Makes a `POST` request to the passed URL.
 
-Use `XMLHttpRequest` web api to make a `post` request to the given `url`.
+Use [`XMLHttpRequest`](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Using_XMLHttpRequest) web api to make a `post` request to the given `url`.
 Set the value of an `HTTP` request header with `setRequestHeader` method.
-Handle the `onload` event, by console logging the `responseText`.
+Handle the `onload` event, by calling the given `callback` the `responseText`.
 Handle the `onerror` event, by running the provided `err` function.
+Omit the third argument, `data`, to send no data to the provided `url`.
+Omit the fourth argument, `err`, to log errors to the console's `error` stream by default.
 
 ```js
-const httpPost = (url, data, err = console.error) => {
+const httpPost = (url, callback, data = null, err = console.error) => {
     const request = new XMLHttpRequest();
     request.open("POST", url, true);
     request.setRequestHeader('Content-type','application/json; charset=utf-8');
-    request.onload = () => console.log(request.responseText);
+    request.onload = () => callback(request.responseText);
     request.onerror = () => err(request);
     request.send(data);
 };
 ```
 
 ```js
-const user = {
-    name: "Foo",
-    password: "fooBar"
+const newPost = {
+  "userId": 1,
+  "id": 1337,
+  "title": "Foo",
+  "body": "bar bar bar"
 };
-const data = JSON.stringify(user);
-httpPost('https://website.com/posts', data, request => {
-  console.log(request.responseText);
-}); // ''
+const data = JSON.stringify(newPost);
+httpPost('https://website.com/posts', console.log, data; /*
+Logs: {
+  "userId": 1,
+  "id": 1337,
+  "title": "Foo",
+  "body": "bar bar bar"
+}
+*/
 ```