minor

Author: iliakan

1-js/04-object-basics/04-object-methods/article.md

@@ -161,7 +161,7 @@ let user = {
 let admin = user;
 user = null; // overwrite to make things obvious
 
-admin.sayHi(); // Woops! inside sayHi(), the old name is used! error!
+admin.sayHi(); // Whoops! inside sayHi(), the old name is used! error!
 ```
 
 If we used `this.name` instead of `user.name` inside the `alert`, then the code would work.

1-js/05-data-types/07-map-set-weakmap-weakset/article.md

@@ -287,7 +287,7 @@ let obj = {};
 weakMap.set(obj, "ok"); // works fine (object key)
 
 *!*
-weakMap.set("test", "Woops"); // Error, because "test" is a primitive
+weakMap.set("test", "Whoops"); // Error, because "test" is a primitive
 */!*
 ```
 

1-js/05-data-types/11-json/article.md

@@ -477,7 +477,7 @@ alert( meetup.date.getDate() ); // Error!
 */!*
 ```
 
-Woops! An error!
+Whoops! An error!
 
 The value of `meetup.date` is a string, not a `Date` object. How `JSON.parse` may know that it should transform that string into a `Date`?
 

1-js/07-object-oriented-programming/10-class-inheritance/article.md

@@ -210,7 +210,7 @@ let rabbit = new Rabbit("White Rabbit", 10); // Error: this is not defined.
 */!*
 ```
 
-Woops! We've got an error. Now we can't create rabbits. What went wrong?
+Whoops! We've got an error. Now we can't create rabbits. What went wrong?
 
 The short answer is: constructors in inheriting classes must call `super(...)`, and (!) do it before using `this`.
 

1-js/08-error-handling/1-try-catch/article.md

@@ -612,7 +612,7 @@ For instance:
 */!*
 
   function readData() {
-    badFunc(); // Woops, something went wrong!
+    badFunc(); // Whoops, something went wrong!
   }
 
   readData();

1-js/08-error-handling/2-custom-errors/article.md

@@ -47,13 +47,13 @@ class ValidationError extends Error {
 }
 
 function test() {
-  throw new ValidationError("Woops!");
+  throw new ValidationError("Whoops!");
 }
 
 try {
   test();
 } catch(err) {
-  alert(err.message); // Woops!
+  alert(err.message); // Whoops!
   alert(err.name); // ValidationError
   alert(err.stack); // a list of nested calls with line numbers for each
 }

8-async/03-promise-chaining/article.md

@@ -110,7 +110,36 @@ Now we have the same 1 -> 2 > 4 output, but with 1 second delay between each.
 
 When we return `new Promise(…)`, the next `.then` in the chain is executed when it settles and gets its result.
 
-Let's use it to `loadScript` multiple scripts one by one:
+Let's use it with `loadScript` to load multiple scripts one by one, in sequence:
+
+```js run
+loadScript("/article/promise-chaining/one.js")
+  .then(function(script) {
+    return loadScript("/article/promise-chaining/two.js");
+  })
+  .then(function(script) {
+    return loadScript("/article/promise-chaining/three.js");
+  })
+  .then(function(script) {
+    // use variables declared in scripts
+    // to show that they indeed loaded
+    alert("Done: " + (one + two + three));
+  });
+```
+
+
+The code totally evades the pyramid of doom. We can add more asynchronous actions to the chain, and the code is still "flat".
+
+## Error handling
+
+In case of an error, the closest `onRejected` handler down the chain is called.
+
+Let's recall that a rejection (error) handler may be assigned with two syntaxes:
+
+- `.then(...,onRejected)`, as a second argument of `.then`.
+- `.catch(onRejected)`, a shorthand for `.then(null, onRejected)`.
+
+In the example below we use the second syntax to catch all errors in the script load chain:
 
 ```js run
 function loadScript(src) {  
@@ -119,13 +148,17 @@ function loadScript(src) {
     script.src = src;
 
     script.onload = () => resolve(script);
-    script.onerror = () => reject(new Error("Script load error: " + src));
+*!*
+    script.onerror = () => reject(new Error("Script load error: " + src)); // (*)
+*/!*
 
     document.head.append(script);
   });
 }
 
-loadScript("/article/promise-chaining/one.js")
+*!*
+loadScript("/article/promise-chaining/ERROR.js")
+*/!*
   .then(function(script) {
     return loadScript("/article/promise-chaining/two.js");
   })
@@ -136,10 +169,53 @@ loadScript("/article/promise-chaining/one.js")
     // use variables declared in scripts
     // to show that they indeed loaded
     alert("Done: " + (one + two + three));
+  })
+*!*
+  .catch(function(error) { // (**)
+    alert(error.message);
   });
+*/!*
 ```
 
-The code totally evades the pyramid of doom. We can add more asynchronous actions to the chain, and the code is still "flat".
+In the code above the first `loadScript` call fails, because `ERROR.js` doesn't exist. The initial error is generated in the line `(*)`, then the first error handler in the chain is called, that is `(**)`.
+
+Now the same thing, but the error occurs in the second script:
+
+
+```js run
+loadScript("/article/promise-chaining/one.js")
+  .then(function(script) {
+*!*
+    return loadScript("/article/promise-chaining/ERROR.js");
+*/!*
+  })
+  .then(function(script) {
+    return loadScript("/article/promise-chaining/three.js");
+  })
+  .then(function(script) {
+    // use variables declared in scripts
+    // to show that they indeed loaded
+    alert("Done: " + (one + two + three));
+  })
+*!*
+  .catch(function(error) {
+    alert(error.message);
+  });
+*/!*
+```
+
+Once again, the `.catch` handles it.
+
+**Throwing an exception is also considered an error.**
+
+For instance:
+
+```js run
+new Promise(function(resolve, reject) {
+  throw new Error("Woops!");
+}).catch(function(error) {
+  alert(error.message); // Whoops
+});
 
 ## Inheriting from promise, thenables, error handling?
 

8-async/03-promise-chaining/head.html

@@ -1,10 +1,13 @@
 <script>
-function loadImage(src) {
-  return new Promise((resolve, reject) => {
-    let img = document.createElement('img');
-    img.src = src;
-    img.onload = () => resolve(img);
-    img.onerror = () => reject(new Error("Image load failed: " + src));
+function loadScript(src) {
+  return new Promise(function(resolve, reject) {
+    let script = document.createElement('script');
+    script.src = src;
+
+    script.onload = () => resolve(script);
+    script.onerror = () => reject(new Error("Script load error: " + src));
+
+    document.head.append(script);
   });
 }
 </script>