doc: added documentation for input type=file

content/docs/forms.md

@@ -189,6 +189,21 @@ Overall, this makes it so that `<input type="text">`, `<textarea>`, and `<select
 >```js
 ><select multiple={true} value={['B', 'C']}>
 >```
+## The file input Tag
+
+In HTML, an `<input type="file">` lets the user choose one or more files from their device storage to be uploaded to a server or manipulated by JavaScript via the [File API](https://developer.mozilla.org/en-US/docs/Web/API/File/Using_files_from_web_applications).
+
+```html
+<input type="file" />
+```
+
+In React, an `<input type="file" />` works similarly to a normal `<input/>` with one important difference: **it is read-only**. (You can't set the value programmatically.) Instead, you should use the File API to interact with the files.
+
+The following example shows how a `ref` can be used to access file(s) in a submit handler:
+
+`embed:forms/input-type-file.js`
+
+[Try it on CodePen](codepen://forms/input-type-file)
 
 ## Handling Multiple Inputs
 

examples/forms/input-type-file.js

@@ -0,0 +1,44 @@
+class FileInput extends React.Component {
+  constructor(props) {
+    super(props);
+    this.handleSubmit = this.handleSubmit.bind(
+      this
+    );
+  }
+  // highlight-range{5}
+  handleSubmit(event) {
+    event.preventDefault();
+    alert(
+      `Selected file - ${
+        this.fileInput.files[0].name
+      }`
+    );
+  }
+
+  render() {
+    return (
+      <form
+        onSubmit={this.handleSubmit}>
+        <label>
+          Upload file:
+          {/* highlight-range{1-6} */}
+          <input
+            type="file"
+            ref={input => {
+              this.fileInput = input;
+            }}
+          />
+        </label>
+        <br />
+        <button type="submit">
+          Submit
+        </button>
+      </form>
+    );
+  }
+}
+
+ReactDOM.render(
+  <FileInput />,
+  document.getElementById('root')
+);