update some charactors to [Jun 28, 2020]

leviding · leviding · commit 2adb7dca8744 · 2020-07-01T17:44:20.000+08:00
diff --git a/1-js/02-first-steps/15-function-basics/article.md b/1-js/02-first-steps/15-function-basics/article.md
@@ -214,36 +214,48 @@ function showMessage(from, text = anotherFunction()) {
 在上面的例子中，每次 `showMessage()` 不带 `text` 参数被调用时，`anotherFunction()` 就会被调用。
 ```
 
-````smart header="旧式默认参数"
-旧版本的 JavaScript 不支持默认参数。所以在大多数旧版本的脚本中，你能找到其他设置默认参数的方法。
+### Alternative default parameters
 
-例如，用于 `undefined` 的显式检查：
+Sometimes it makes sense to set default values for parameters not in the function declaration, but at a later stage, during its execution.
 
-```js
-function showMessage(from, text) {
+To check for an omitted parameter, we can compare it with `undefined`:
+
+```js run
+function showMessage(text) {
 *!*
   if (text === undefined) {
-    text = 'no text given';
+    text = 'empty message';
   }
 */!*
 
-  alert( from + ": " + text );
+  alert(text);
 }
+
+showMessage(); // empty message
 ```
 
-……或使用 `||` 运算符：
+...Or we could use the `||` operator:
 
 ```js
-function showMessage(from, text) {
-  // 如果 text 能转为 false，那么 text 会得到“默认”值
-  text = text || 'no text given';
+// if text parameter is omitted or "" is passed, set it to 'empty'
+function showMessage(text) {
+  text = text || 'empty';
   ...
 }
 ```
 
+Modern JavaScript engines support the [nullish coalescing operator](info:nullish-coalescing-operator) `??`, it's better when falsy values, such as `0`, are considered regular:
 
-````
+```js run
+// if there's no "count" parameter, show "unknown"
+function showCount(count) {
+  alert(count ?? "unknown");
+}
 
+showCount(0); // 0
+showCount(null); // unknown
+showCount(); // unknown
+```
 
 ## 返回值
 
diff --git a/1-js/02-first-steps/18-javascript-specials/article.md b/1-js/02-first-steps/18-javascript-specials/article.md
@@ -152,6 +152,9 @@ JavaScript 支持以下运算符：
 逻辑运算符
 : 逻辑与 `&&` 和或 `||` 执行短路运算，然后返回运算停止处的值（`true`/`false` 不是必须的）。逻辑非 `!` 将操作数转换为布尔值并返回其相反的值。
 
+Nullish coalescing operator
+: The `??` operator provides a way to choose a defined value from a list of variables. The result of `a ?? b` is `a` unless it's `null/undefined`, then `b`.
+
 比较运算符
 : 对不同类型的值进行相等检查时，运算符 `==` 会将不同类型的值转换为数字（除了 `null` 和 `undefined`，它们彼此相等而没有其他情况），所以下面的例子是相等的：
 
@@ -171,7 +174,7 @@ JavaScript 支持以下运算符：
 其他运算符
 : 还有很少一部分其他运算符，如逗号运算符。
 
-更多内容：<info:operators>，<info:comparison>，<info:logical-operators>。
+更多内容：<info:operators>，<info:comparison>，<info:logical-operators>，<info:nullish-coalescing-operator>。
 
 ## 循环
 
@@ -213,6 +216,7 @@ let age = prompt('Your age?', 18);
 switch (age) {
   case 18:
     alert("Won't work"); // prompt 的结果是一个字符串，而不是数字
+    break;
 
   case "18":
     alert("This works!");
diff --git a/1-js/03-code-quality/02-coding-style/article.md b/1-js/03-code-quality/02-coding-style/article.md
@@ -285,7 +285,7 @@ function pow(x, n) {
 
 一些受欢迎的选择：
 
-- [Google JavaScript 风格指南](https://google.github.io/styleguide/javascriptguide.xml)
+- [Google JavaScript 风格指南](https://google.github.io/styleguide/jsguide.html)
 - [Airbnb JavaScript 风格指南](https://github.com/airbnb/javascript)
 - [Idiomatic.JS](https://github.com/rwaldron/idiomatic.js)
 - [StandardJS](https://standardjs.com/)
diff --git a/1-js/03-code-quality/04-ninja-code/article.md b/1-js/03-code-quality/04-ninja-code/article.md
@@ -43,7 +43,7 @@ i = i ? i < 0 ? Math.max(0, len + i) : i : 0;
 ```
 
 
-另一个提高编程速度的方法是，到处使用单字母的变量名。例如 `a`、`b` 或 `c`。
+另一个缩减代码量的方法是，到处使用单字母的变量名。例如 `a`、`b` 或 `c`。
 
 短变量就像森林中真正的忍者一样，一下就找不到了。没有人能够通过编辑器的“搜索”功能找到它。即使有人做到了，他也不能“破译”出变量名 `a` 或 `b` 到底是什么意思。
 
diff --git a/1-js/03-code-quality/05-testing-mocha/beforeafter.view/test.js b/1-js/03-code-quality/05-testing-mocha/beforeafter.view/test.js
@@ -1,5 +1,11 @@
 describe("test", function() {
+  
+   // Mocha usually waits for the tests for 2 seconds before considering them wrong
+  
+  this.timeout(200000); // With this code we increase this - in this case to 200,000 milliseconds
 
+  // This is because of the "alert" function, because if you delay pressing the "OK" button the tests will not pass!
+  
   before(() => alert("Testing started – before all tests"));
   after(() => alert("Testing finished – after all tests"));
 
diff --git a/1-js/04-object-basics/01-object/4-const-object/solution.md b/1-js/04-object-basics/01-object/4-const-object/solution.md
diff --git a/1-js/04-object-basics/01-object/4-const-object/task.md b/1-js/04-object-basics/01-object/4-const-object/task.md
diff --git a/1-js/04-object-basics/01-object/article.md b/1-js/04-object-basics/01-object/article.md
@@ -92,6 +92,30 @@ let user = {
 ```
 这叫做尾随（trailing）或悬挂（hanging）逗号。这样便于我们添加、删除和移动属性，因为所有的行都是相似的。
 
+````smart header="Object with const can be changed"
+Please note: an object declared as `const` *can* be modified.
+
+For instance:
+
+```js run
+const user = {
+  name: "John"
+};
+
+*!*
+user.name = "Pete"; // (*)
+*/!*
+
+alert(user.name); // Pete
+```
+
+It might seem that the line `(*)` would cause an error, but no. The `const` fixes the value of `user`, but not its contents.
+
+The `const` would give an error only if we try to set `user=...` as a whole.
+
+There's another way to make constant object properties, we'll cover it later in the chapter <info:property-descriptors>.
+````
+
 ## 方括号
 
 对于多词属性，点操作就不能用了：
