minor

Author: iliakan

1-js/11-async/06-promisify/article.md

@@ -2,8 +2,6 @@
 
 Promisification -- is a long word for a simple transform. It's conversion of a function that accepts a callback into a function returning a promise.
 
-To be more precise, we create a wrapper-function that does the same, internally calling the original one, but returns a promise.
-
 Such transforms are often needed in real-life, as many functions and libraries are callback-based. But promises are more convenient. So it makes sense to promisify those.
 
 For instance, we have `loadScript(src, callback)` from the chapter <info:callbacks>.
@@ -23,7 +21,7 @@ function loadScript(src, callback) {
 // loadScript('path/script.js', (err, script) => {...})
 ```
 
-Let's promisify it. The new `loadScriptPromise(src)` function will do the same, but accept only `src` (no callback) and return a promise.
+Let's promisify it. The new `loadScriptPromise(src)` function will do the same, but accept only `src` (no `callback`) and return a promise.
 
 ```js
 let loadScriptPromise = function(src) {
@@ -39,13 +37,13 @@ let loadScriptPromise = function(src) {
 // loadScriptPromise('path/script.js').then(...)
 ```
 
-Now `loadScriptPromise` fits well in our promise-based code.
+Now `loadScriptPromise` fits well in promise-based code.
 
 As we can see, it delegates all the work to the original `loadScript`, providing its own callback that translates to promise `resolve/reject`.
 
-As we may need to promisify many functions, it makes sense to use a helper.
+In practice we'll probably need to promisify many functions, it makes sense to use a helper.
 
-That's actually very simple -- `promisify(f)` below takes a to-promisify function `f` and returns a wrapper function.
+We'll call it `promisify(f)`: it accepts a to-promisify function `f` and returns a wrapper function.
 
 That wrapper does the same as in the code above: returns a promise and passes the call to the original `f`, tracking the result in a custom callback:
 
@@ -61,7 +59,7 @@ function promisify(f) {
         }
       }
 
-      args.push(callback); // append our custom callback to the end of arguments
+      args.push(callback); // append our custom callback to the end of f arguments
 
       f.call(this, ...args); // call the original function
     });
@@ -75,9 +73,9 @@ loadScriptPromise(...).then(...);
 
 Here we assume that the original function expects a callback with two arguments `(err, result)`. That's what we encounter most often. Then our custom callback is in exactly the right format, and `promisify` works great for such a case.
 
-But what if the original `f` expects a callback with more arguments `callback(err, res1, res2)`?
+But what if the original `f` expects a callback with more arguments `callback(err, res1, res2, ...)`?
 
-Here's a modification of `promisify` that returns an array of multiple callback results:
+Here's a more advanced version of `promisify`: if called as `promisify(f, true)`, the promise result will be an array of callback results `[res1, res2, ...]`:
 
 ```js
 // promisify(f, true) to get array of results
@@ -105,7 +103,7 @@ f = promisify(f, true);
 f(...).then(arrayOfResults => ..., err => ...)
 ```
 
-In some cases, `err` may be absent at all: `callback(result)`, or there's something exotic in the callback format, then we can promisify such functions without using the helper, manually.
+For more exotic callback formats, like those without `err` at all: `callback(result)`, we can promisify such functions without using the helper, manually.
 
 There are also modules with a bit more flexible promisification functions, e.g. [es6-promisify](https://github.com/digitaldesignlabs/es6-promisify). In Node.js, there's a built-in `util.promisify` function for that.