Update "File and FileReader" article

Author: odsantos

4-binary/04-file/article.md

@@ -1,6 +1,6 @@
 # File and FileReader
 
-A [File](https://www.w3.org/TR/FileAPI/#dfn-file) object inhereits from `Blob`, but is extended with filesystem-related capabilities.
+A [File](https://www.w3.org/TR/FileAPI/#dfn-file) object inherits from `Blob` and is extended with filesystem-related capabilities.
 
 There are two ways to obtain it.
 
@@ -10,14 +10,18 @@ First, there's a constructor, similar to `Blob`:
 new File(fileParts, fileName, [options])
 ```
 
-- **`fileParts`** -- is an array of Blob/BufferSource/String value, same as `Blob`.
+- **`fileParts`** -- is an array of Blob/BufferSource/String values.
 - **`fileName`** -- file name string.
 - **`options`** -- optional object:
-    - **`lastModified`** -- a timestamp (integer date) of last modification.
+    - **`lastModified`** -- the timestamp (integer date) of last modification.
 
-Second, more often we get a file from `<input type="file">` or drag'n'drop or other browser interfaces. Then the file gets these from OS.
+Second, more often we get a file from `<input type="file">` or drag'n'drop or other browser interfaces. In that case, the file gets this information from OS.
 
-For instance:
+As `File` inherits from `Blob`, `File` objects have the same properties, plus:
+- `name` -- the file name,
+- `lastModified` -- the timestamp of last modification.
+
+That's how we can get a `File` object from `<input type="file">`:
 
 ```html run
 <input type="file" onchange="showFile(this)">
@@ -38,9 +42,9 @@ The input may select multiple files, so `input.files` is an array-like object wi
 
 ## FileReader
 
-[FileReader](https://www.w3.org/TR/FileAPI/#dfn-filereader) is an object with the sole purpose of reading from `Blob` (and hence `File` too) objects.
+[FileReader](https://www.w3.org/TR/FileAPI/#dfn-filereader) is an object with the sole purpose of reading data from `Blob` (and hence `File` too) objects.
 
-It's event based, as reading from disk may take time.
+It delivers the data using events, as reading from disk may take time.
 
 The constructor:
 
@@ -50,9 +54,9 @@ let reader = new FileReader(); // no arguments
 
 The main methods:
 
-- **`readAsArrayBuffer(blob)`** -- read the data as `ArrayBuffer`
-- **`readAsText(blob, [encoding])`** -- read the data as a string (encoding is `utf-8` by default)
-- **`readAsDataURL(blob)`** -- encode the data as base64 data url.
+- **`readAsArrayBuffer(blob)`** -- read the data in binary format `ArrayBuffer`.
+- **`readAsText(blob, [encoding])`** -- read the data as a text string with the given encoding (`utf-8` by default).
+- **`readAsDataURL(blob)`** -- read the binary data and encode it as base64 data url.
 - **`abort()`** -- cancel the operation.
 
 The choice of `read*` method depends on which format we prefer, how we're going to use the data.
@@ -66,7 +70,7 @@ As the reading proceeds, there are events:
 - `progress` -- occurs during reading.
 - `load` -- no errors, reading complete.
 - `abort` -- `abort()` called.
-- `error` -- error has occured.
+- `error` -- error has occurred.
 - `loadend` -- reading finished with either success or failure.
 
 When the reading is finished, we can access the result as:
@@ -101,28 +105,28 @@ function readFile(input) {
 ```
 
 ```smart header="`FileReader` for blobs"
-As mentioned in the chapter <info:blob>, `FileReader` works for any blobs, not just files.
+As mentioned in the chapter <info:blob>, `FileReader` can read not just files, but any blobs.
 
-So we can use it to convert a blob to another format:
+We can use it to convert a blob to another format:
 - `readAsArrayBuffer(blob)` -- to `ArrayBuffer`,
 - `readAsText(blob, [encoding])` -- to string (an alternative to `TextDecoder`),
 - `readAsDataURL(blob)` -- to base64 data url.
 ```
 
 
-```smart header="`FileReaderSync` is available for workers only"
+```smart header="`FileReaderSync` is available inside Web Workers"
 For Web Workers, there also exists a synchronous variant of `FileReader`, called [FileReaderSync](https://www.w3.org/TR/FileAPI/#FileReaderSync).
 
 Its reading methods `read*` do not generate events, but rather return a result, as regular functions do.
 
-That's only inside a Web Worker though, because delays and hang-ups in Web Workers are less important, they do not affect the page.
+That's only inside a Web Worker though, because delays in synchronous calls, that are possible while reading from files, in Web Workers are less important. They do not affect the page.
 ```
 
 ## Summary
 
-`File` object inherit from `Blob`.
+`File` objects inherit from `Blob`.
 
-In addition to `Blob` methods and properties, `File` objects also have `fileName` and `lastModified` properties, plus the internal ability to read from filesystem. We usually get `File` objects from user input, like `<input>` or drag'n'drop.
+In addition to `Blob` methods and properties, `File` objects also have `name` and `lastModified` properties, plus the internal ability to read from filesystem. We usually get `File` objects from user input, like `<input>` or Drag'n'Drop events (`ondragend`).
 
 `FileReader` objects can read from a file or a blob, in one of three formats:
 - String (`readAsText`).
@@ -131,4 +135,4 @@ In addition to `Blob` methods and properties, `File` objects also have `fileName
 
 In many cases though, we don't have to read the file contents. Just as we did with blobs, we can create a short url with `URL.createObjectURL(file)` and assign it to `<a>` or `<img>`. This way the file can be downloaded or shown up as an image, as a part of canvas etc.
 
-And if we're going to send a `File` over a network, that's also easy, as network API like `XMLHttpRequest` or `fetch` natively accepts `File` objects.
+And if we're going to send a `File` over a network, that's also easy: network API like `XMLHttpRequest` or `fetch` natively accepts `File` objects.