[ Deepak Grover,Hanu Prateek Kunduru]ES6 for Humans

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1. ES6 for Humans: The Latest Standard of JavaScript: ES2015 and Beyond
   
2. Authors: Deepak Grover – Hanu Prateek Kunduru
   
3. 
   
4. ISBN-10 书号: 1484226224
   
5. ISBN-13 书号: 9781484226223
   
6. Edition: 1st ed.
   
7. Release 出版日期: 2017-08-17
   
8. pages 页数: (137)
   
9. 39.99
   
10. 
    
11. Book Description
    
12. Learn ES6 best practices for code optimization and organization and walk through practical, common examples of how to implement complete components of your applications. While this book covers the basic concepts of modern JavaScript, it primarily focuses on the new syntax, data-types, functionalities, and everything else that’s new in ES6, the latest standard of JavaScript.
    
13. 
    
14. You’ll examine how to use ES6 in functional programming and explore the new more modular and object-oriented approach to JavaScript. This book will help you sharpen and upgrade your JavaScript language skills so you to easily explore modern ES6 based frameworks or libraries such as ReactJS, ReactNative, Angular4 and Vue.js.
    
15. 
    
16. ES6 for Humans is a complete guide to writing ES6 and will enable you to start taking advantage of this exciting new version of JavaScript.
    
17. 
    
18. What You’ll Learn
    
19. Use all the new features added to JavaScript
    
20. Compare ES5 and ES6 in varied situations
    
21. Refresh your core JavaScript fundamentals
    
22. Understand the modular and object-oriented approach to JavaScript
    
23. Who this Book Is For
    
24. Any Javascript developer who wants to fully understand and dive into the new features of ES6/ES2015.
    
25. 
    
26. Developers with some background in programming, preferably in JavaScript.
    
27. 
    
28. A basic understanding of coding concepts and exposure to object-oriented programming is expected.
    
29. 
    
30. Contents
    
31. Chapter 1: Getting Started with ES6
    
32. Chapter 2: New Syntax in ES6
    
33. Chapter 3: Destructuring
    
34. Chapter 4: Classes in ES6
    
35. Chapter 5: Modules
    
36. Chapter 6: Symbols in ES6
    
37. Chapter 7: Arrays and Collections
    
38. Chapter 8: Iterators and Generators
    
39. Chapter 9: Promises in ES6
    
40. Chapter 10: Meta Programming
    
41. Chapter 11: Beyond ES6

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1. Symbols and Registry
   
2. So far, we have talked about local symbols and how you can access them by obtaining
   
3. a reference. Symbols can also be placed in a global registry, from where they can be
   
4. accessed across different contexts known as realms. A realm is a context in which pieces
   
5. of code exist such as the page your application is running in, or an <iframe> within your
   
6. page, or a web worker with their context containing global variables and loaded modules.
   
7. Symbols come with a special power to be available throughout the runtime-wide
   
8. symbol registry, and you can use the following methods to add symbols to the runtimewide
   
9. symbol registry:
   
10. Symbol.for(key) and Symbol.keyFor(symbol).

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1. Symbol.keyFor(symbol)
   
2. Symbol.keyFor(symbol) retrieves the key from the global symbol registry that was
   
3. associated with the given symbol when the symbol was added to the registry. It returns
   
4. undefined when the symbol is not found in the registry.
   
5. const symbol = Symbol.for('myHouse');
   
6. console.log(Symbol.keyFor(symbol)); // myHouse
   
7. const myCat = Symbol();
   
8. Symbol.keyFor(myCat); // undefined

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1. Built-In Symbols
   
2. ES6 comes with a range of symbols that are predefined in the language specification,
   
3. most of which expose some meta properties and behaviors of JavaScript objects. Some of
   
4. the well-known symbols are the following:
   
5. Symbol.hasInstance - which allows us to determine whether an object is the
   
6. instance of the constructor. It is called by instanceof operator internally.

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1. const customers = {
   
2. '0': 'matt',
   
3. '1': 'ian',
   
4. '2': 'mikhail',
   
5. '3': 'akia',
   
6. '4': 'vincent',
   
7. length: 5
   
8. };
   
9. Now, if we were to convert this object into an array, we can do it using the Array.
   
10. from() syntax simply like this:
    
11. Array.from(customers).forEach(customer => {
    
12. console.log(customer);
    
13. });
    
14. In this example, we just passed into the function the customer object, and in turn it
    
15. returns an array formed from the individual elements. Let’s look at the specific Array.from
    
16. syntax:
    
17. Array.from(arrayLike[, mapFn[, thisArg]])

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1. Array.of()
   
2. Another really handy method introduced in ES6 is Array.of(), which lets you create an
   
3. array of elements easily. Array.of() takes a list of items as parameters and returns them
   
4. to you as an array. Consider the following example,
   
5. let arr = Array.of(10, 20, 30, 40);
   
6. console.log(arr); // [10, 20, 30, 40]
   
7. You might be wondering how is this different from the traditional Array(...)
   
8. constructor. You can also create an array with the array constructor method using the
   
9. Array() syntax. But, the difference between Array.of() and the Array constructor is
   
10. the way they handle a single number as an argument. The Array constructor has a very
    
11. weird behavior where if only one number is passed to it, instead of making an array of
    
12. one element with that number value, it constructs an empty array with the number as its
    
13. length. All the elements are set to undefined.
    
14. The Array.of() static method fixes this issue and is now the preferred function-form
    
15. constructor for arrays.
    
16. Take a look at the following example:
    
17. const arr1 = Array.of(10);
    
18. console.log(arr1); // [10]
    
19. console.log(arr1.length); // 1
    
20. const arr2 = Array(10);
    
21. console.log(arr2); // [,,,,,,,,,]
    
22. console.log(arr2.length); // 10

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1. Array.prototype.keys( )
   
2. This method returns a new Array Iterator that contains the keys for each index in the array:
   
3. const breakfast = ['apples', 'bananas', 'oranges'];
   
4. const kBreakfast = breakfast.keys();
   
5. console.log(kBreakfast.next().value); // 0
   
6. console.log(kBreakfast.next().value); // 1
   
7. console.log(kBreakfast.next().value); // 2

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1. Array.prototype.values( )
   
2. This method returns a new Array Iterator object that contains the values for each index in
   
3. the array:
   
4. const breakfast = ['apples', 'bananas', 'oranges'];
   
5. const vBreakfast = breakfast.values();
   
6. console.log(vBreakfast.next().value); // apples
   
7. console.log(vBreakfast.next().value); // bananas
   
8. console.log(vBreakfast.next().value); // oranges

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1. Array.prototype.findIndex( )
   
2. This method is an equivalent of find(). Instead of returning an item, this method
   
3. returns the index position. If none of the elements in the collection match the callback
   
4. (element, index, array) criteria, the return value is -1.
   
5. Consider the following code snippet, for example:
   
6. result = inventory.findIndex((fruit) => fruit.name === 'apples');
   
7. console.log(result); // 0
   
8. result = inventory.findIndex((fruit) => fruit.name === 'grapes');
   
9. console.log(result); // -1
   
10. This method is similar to the indexOf()method from ES5, which simply locates
    
11. the element in the array. With the indexOf() method, you can only search for an
    
12. element inside an array; it doesn’t support a callback method. Whereas in case of the
    
13. findIndex()method, we have the capability to apply a condition to which the element at
    
14. the returned index position must satisfy.

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1. Array.prototype.copyWithin( )
   
2. The copyWithin()method copies the sequence of array elements within the array to
   
3. the position starting at target. The elements that should be copied are taken from the
   
4. (start, end) range. The start argument is optional and defaults to 0. Also, the end
   
5. argument is also optional and defaults to the length of the array.
   
6. The syntax of copyWithin() method looks like this:
   
7. Array.prototype.copyWithin(target, start = 0, end = this.length)
   
8. Let’s start with a simple example. Consider the following code snippet:
   
9. let fruits = ["apples", "bananas", "oranges", "grapes", "guava",
   
10. "watermelon"];
    
11. fruits.copyWithin(4);
    
12. console.log(fruits);
    
13. // ["apples", "bananas", "oranges", "grapes", "apples", "bananas"]

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