Merge pull request #2 from basarat/master

update from upstream

Author: spences10

.gitignore

@@ -1,6 +1,11 @@
-.alm
+# Mac 
 *.DS_Store
 
+# IDEs
+.alm
+.vscode
+
+
 # Node rules:
 ## Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
 .grunt

README.md

@@ -1,7 +1,7 @@
 TypeScript Deep Dive
 =======
 
-I've been looking at the issues that turn up commonly when people start using TypeScript. This is based on the lessons from [StackOverflow](http://stackoverflow.com/tags/typescript/topusers) / [DefinitelyTyped](https://github.com/DefinitelyTyped/) and general engagement with the [TypeScript community](https://github.com/TypeStrong/). You can [follow for updates](https://twitter.com/basarat) and [don't forget to ★ on Github](https://github.com/basarat/typescript-book) 🌹
+I've been looking at the issues that turn up commonly when people start using TypeScript. This is based on the lessons from [Stack Overflow](http://stackoverflow.com/tags/typescript/topusers) / [DefinitelyTyped](https://github.com/DefinitelyTyped/) and general engagement with the [TypeScript community](https://github.com/TypeStrong/). You can [follow for updates](https://twitter.com/basarat) and [don't forget to ★ on GitHub](https://github.com/basarat/typescript-book) 🌹
 
 ## Reviews
 
@@ -22,20 +22,27 @@ I've been looking at the issues that turn up commonly when people start using Ty
 * Guyz excellent book on Typescript(@typescriptlang) by @basarat ([link](https://twitter.com/deeinlove/status/813245965507260417))
 * Leaning on the legendary @basarat's "TypeScript Deep Dive" book heavily at the moment ([link](https://twitter.com/sitapati/status/814379404956532737))
 * numTimesPointedPeopleToBasaratsTypeScriptBook++; ([link](https://twitter.com/brocco/status/814227741696462848))
-* A book not only for typescript, a good one for deeper javascript knowledge as well. [link](https://www.gitbook.com/book/basarat/typescript/discussions/59)
+* A book not only for typescript, a good one for deeper JavaScript knowledge as well. [link](https://www.gitbook.com/book/basarat/typescript/discussions/59)
 * In my new job, we're using @typescriptlang, which I am new to. This is insanely helpful huge thanks, @basarat! [link](https://twitter.com/netchkin/status/855339390566096896)
 * Thank you for writing TypeScript Deep Dive. I have learned so much. [link](https://twitter.com/buctwbzs/status/857198618704355328?refsrc=email&s=11)
 * Loving @basarat's @typescriptlang online book basarat.gitbooks.io/typescript/# loaded with great recipes! [link](https://twitter.com/ericliprandi/status/857608837309677568)
 * Microsoft doc is great already, but if want to "dig deeper" into TypeScript I find this book of great value  [link](https://twitter.com/caludio/status/876729910550831104)
 * Thanks, this is a great book 🤓🤓 [link](https://twitter.com/jjwonmin/status/885666375548547073)
 * Deep dive to typescript is awesome in so many levels. i find it very insightful. Thanks [link](https://twitter.com/orenmizr/status/891083492787970053)
+* @basarat's intro to @typescriptlang is still one of the best going (if not THE best) [link](https://twitter.com/stevealee/status/953953255968698368)
+* This is sweet! So many #typescript goodies! [link](https://twitter.com/pauliescanlon/status/989898852474998784)
 
 ## Get Started
 If you are here to read the book online [get started](http://basarat.gitbooks.io/typescript/content/docs/getting-started.html).
 
+## Translations 
+Book is completely free so you can copy paste whatever you want without requiring permission. If you have a translation you want me to link here. [Send a PR](https://github.com/basarat/typescript-book/edit/master/README.md).
+* [Filipino](https://github.com/themarshann/typescript-book-fil)
+* [Italian](https://github.com/TizioFittizio/typescript-book)
+
 ## Other Options
 You can also download one of the following:
-* [EPUB for iPad,iPhone,Mac](https://www.gitbook.com/download/epub/book/basarat/typescript)
+* [EPUB for iPad, iPhone, Mac](https://www.gitbook.com/download/epub/book/basarat/typescript)
 * [PDF for Windows and others](https://www.gitbook.com/download/pdf/book/basarat/typescript)
 * [MOBI for Kindle](https://www.gitbook.com/download/mobi/book/basarat/typescript)
 

SUMMARY.md

@@ -12,7 +12,6 @@
 * [Future JavaScript Now](docs/future-javascript.md)
   * [Classes](docs/classes.md)
     * [Classes Emit](docs/classes-emit.md)
-    * [Classes Super](docs/classes-super.md)
   * [Arrow Functions](docs/arrow-functions.md)
   * [Rest Parameters](docs/rest-parameters.md)
   * [let](docs/let.md)
@@ -61,12 +60,24 @@
   * [Index Signatures](docs/types/index-signatures.md)
   * [Moving Types](docs/types/moving-types.md)
   * [Exception Handling](docs/types/exceptions.md)
+  * [Mixins](docs/types/mixins.md)
 * [JSX](docs/jsx/tsx.md)
+  * [React](docs/jsx/react.md)
+  * [Non React JSX](docs/jsx/others.md)
 * [Options](docs/options/intro.md)
   * [noImplicitAny](docs/options/noImplicitAny.md)
   * [strictNullChecks](docs/options/strictNullChecks.md)
+* [Errors in TypeScript](docs/errors/main.md)
+  * [Interpreting Errors](docs/errors/interpreting-errors.md)
+  * [Common Errors](docs/errors/common-errors.md)
+* [Testing](docs/testing/intro.md)
+  * [Jest](docs/testing/jest.md)
+  * [Cypress](docs/testing/cypress.md)
+* [Tools](docs/tools/intro.md)
+  * [Prettier](docs/tools/prettier.md)
+  * [Husky](docs/tools/husky.md)
+  * [Changelog](docs/tools/changelog.md)
 * [TIPs](docs/tips/main.md)
-  * [Quick Object Return](docs/tips/quickObjectReturn.md)
   * [String Based Enums](docs/tips/stringEnums.md)
   * [Nominal Typing](docs/tips/nominalTyping.md)
   * [Stateful Functions](docs/tips/statefulFunctions.md)
@@ -77,7 +88,6 @@
   * [Classes are Useful](docs/tips/classesAreUseful.md)
   * [Avoid Export Default](docs/tips/defaultIsBad.md)
   * [Limit Property Setters](docs/tips/propertySetters.md)
-  * [`null` is bad](docs/tips/null.md)
   * [`outFile` caution](docs/tips/outFile.md)
   * [JQuery tips](docs/tips/jquery.md)
   * [static constructors](docs/tips/staticConstructor.md)
@@ -89,7 +99,6 @@
   * [Create Arrays](docs/tips/create-arrays.md)
   * [Typesafe Event Emitter](docs/tips/typed-event.md)
 * [StyleGuide](docs/styleguide/styleguide.md)
-* [Common Errors](docs/errors/main.md)
 * [TypeScript Compiler Internals](docs/compiler/overview.md)
   * [Program](docs/compiler/program.md)
   * [AST](docs/compiler/ast.md)

book.json

@@ -1,4 +1,7 @@
 {
+  "language": "en",
+  "author": "Basarat Ali Syed",
+  "title": "TypeScript Deep Dive",
   "plugins": ["edit-link", "github", "adsense","header"],
   "pluginsConfig": {
     "layout": {

code/errors/errors.ts renamed to code/errors/common-errors.ts

@@ -0,0 +1,21 @@
+export const module = 123;
+
+type SomethingComplex = {
+  foo: number,
+  bar: string
+}
+function takeSomethingComplex(arg: SomethingComplex) {
+}
+function getBar(): string {
+  return 'some bar';
+}
+
+//////////////////////////////////
+// Example error production
+//////////////////////////////////
+const fail = {
+  foo: 123,
+  bar: getBar
+};
+
+takeSomethingComplex(fail); // TS ERROR HAPPENS HERE 

code/errors/errors.js

@@ -1 +1,5 @@
-{}
+{
+  "compilerOptions": {
+    "noEmit": true
+  }
+}

code/errors/interpreting-errors.ts

@@ -7,7 +7,7 @@ module aaa {
 
   const queue = new Queue();
   queue.push(0);
-  queue.push("1"); // Ops a mistake
+  queue.push("1"); // Oops a mistake
 
   // a developer walks into a bar
   console.log(queue.pop().toPrecision(1));
@@ -68,4 +68,4 @@ namespace ddd {
   function loadUsers() {
     return getJSON<LoadUsersResponse>({ url: 'https://example.com/users' });
   }
-}
+}

code/errors/tsconfig.json

@@ -3,6 +3,7 @@
 * [Tip: Arrow Function Danger](#tip-arrow-function-danger)
 * [Tip: Libraries that use `this`](#tip-arrow-functions-with-libraries-that-use-this)
 * [Tip: Arrow Function inheritance](#tip-arrow-functions-and-inheritance)
+* [Tip: Quick object return](#tip-quick-object-return)
 
 ### Arrow Functions
 
@@ -90,7 +91,7 @@ then `this` is going to be the correct calling context (in this example `person`
 In fact if you want `this` *to be the calling context* you should *not use the arrow function*. This is the case with callbacks used by libraries like jquery, underscore, mocha and others. If the documentation mentions functions on `this` then you should probably just use a `function` instead of a fat arrow. Similarly if you plan to use `arguments` don't use an arrow function.
 
 #### Tip: Arrow functions with libraries that use `this`
-Many libraries do this e.g. `jQuery` iterables (one example http://api.jquery.com/jquery.each/) will use `this` to pass you the object that it is currently iterating over. In this case if you want to access the library passed `this` as well as the surrounding context just use a temp variable like `_self` like you would in the absence of arrow functions.
+Many libraries do this e.g. `jQuery` iterables (one example https://api.jquery.com/jquery.each/) will use `this` to pass you the object that it is currently iterating over. In this case if you want to access the library passed `this` as well as the surrounding context just use a temp variable like `_self` like you would in the absence of arrow functions.
 
 ```ts
 let _self = this;
@@ -101,8 +102,26 @@ something.each(function() {
 ```
 
 #### Tip: Arrow functions and inheritance
+Arrow functions as properties on classes work fine with inheritance: 
 
-If you have an instance method as an arrow function then it goes on `this`. Since there is only one `this` such functions cannot participate in a call to `super` (`super` only works on prototype members). You can easily get around it by creating a copy of the method before overriding it in the child.
+```ts
+class Adder {
+    constructor(public a: number) {}
+    add = (b: number): number => {
+        return this.a + b;
+    }
+}
+class Child extends Adder {
+    callAdd(b: number) {
+        return this.add(b);
+    }
+}
+// Demo to show it works
+const child = new Child(123);
+console.log(child.callAdd(123)); // 246
+```
+
+However, they do not work with the `super` keyword when you try to override the function in a child class. Properties go on `this`. Since there is only one `this` such functions cannot participate in a call to `super` (`super` only works on prototype members). You can easily get around it by creating a copy of the method before overriding it in the child.
 
 ```ts
 class Adder {
@@ -122,3 +141,26 @@ class ExtendedAdder extends Adder {
     }
 }
 ```
+
+### Tip: Quick object return
+
+Sometimes you need a function that just returns a simple object literal. However, something like
+
+```ts
+// WRONG WAY TO DO IT
+var foo = () => {
+    bar: 123
+};
+```
+is parsed as a *block* containing a *JavaScript Label* by JavaScript runtimes (cause of the JavaScript specification).
+
+>  If that doesn't make sense, don't worry, as you get a nice compiler error from TypeScript saying "unused label" anyways. Labels are an old (and mostly unused) JavaScript feature that you can ignore as a modern GOTO (considered bad by experienced developers 🌹)
+
+You can fix it by surrounding the object literal with `()`:
+
+```ts
+// Correct 🌹
+var foo = () => ({
+    bar: 123
+});
+```