Rehan Zaidi [Rehan Zaidi] - JavaScript Essentials for SAP ABAP Developers: A Guide to Mobile and Desktop Application Development
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JavaScript Essentials for SAP ABAP Developers: A Guide to Mobile and Desktop Application Development: summary, description and annotation
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Easily master JavaScript (JS) with this quick guide and develop mobile and desktop applications for SAP Fiori. This book equips ABAP/SAP developers with the essential topics to get started with JS.
The focus of JavaScript Essentials for SAP ABAP Developers is on the parts of the JS language that are useful from the perspective of an ABAP developer. The book starts with a brief intro to HTML, the basics of JS, and how to create and run a simple JS program. It then dives into the details of the language, showing how to make simple programs. It covers loops in detail, mathematical operations, and string and regular expressions in JS, as well as a taste of functions, followed by objects and object-oriented programming in JavaScript. The book provides:
- Sample code and screenshots to help you fully understand JS
- A chapter on JS best practices and recommendations
- Differences and comparisons of the elements and data structures of ABAP and JavaScript to help you quickly master the material
What Youll Learn
- Create and run a simple JavaScript program
- Understand loops, operations, and expressions
- Master the Create and Use functions
- Use objects and object-oriented programming in JS
- Apply the best practices of JS programming
Who This Book Is For
SAP programmers and developers, ABAP users and developers, and university students learning ABAP and JavaScript
Rehan Zaidi [Rehan Zaidi]: author's other books
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Rehan Zaidi 2017
Rehan Zaidi , JavaScript Essentials for SAP ABAP Developers , 10.1007/978-1-4842-2220-1_10
Rehan Zaidi 1
(1) Karachi, Pakistan
This chapter introduces the various ways you can use JavaScript Object Notation. It starts with an overview of JSON and then dives into the details of the data types used in JSON. You will then see how the JSON arrays and objects work in JS programs. Finally, you will see two useful methods, parse and stringify , of the JSON object.
JSON is a form of data representation that lets you arrange interchangeable information in an organized manner. JSON is in text form (human-readable) and resides in a file. The usual file extension associated to JSON files is .json.
Apart from JavaScript, JSON may be used for Java, Python, Perl, etc. JSON may be used to exchange data between a browser and a server.
The syntax of JSON is a subset of JavaScript syntax consisting of data having name and value pairs.
The objects are contained in curly brackets, {}, separated by commas, whereas Objects and each name followed by colon (:). Arrays are contained within square brackets, [], and values are separated by commas.
var Employee = { "name":"Twinkle", "empid":1234, "position":"Trainer", "city":"London" }var Company = { "Employee": [{ "name":"Twinkle", "empid":1234, "position":"Trainer", "city":"London" },{ "name":"John", "empid":4536, "position":"Associate", "city":"Denver" }] }Consider the example presented in Listing .
var empObj;empObj = { "name":"Kelvin Desouza", "empId":17924, "designation":"Trainer", "city":"London" };console.log(empObj.name + " " + empObj.empId);In this code, you can see the creation of an object with JavaScript using JSON-like syntax. This example declares the variable named empObj , assigns to it some name/value pairs, and then accesses the objects values using dot notation. Only the employee name and ID are specified in the console.log method, so only those two values will be displayed in the web browser console.
The output of Listing .
JSON has the following data types:
Number: Numbers in JSON cannot appear within quotes, and are usually integer or floating point. For example:
{ "empid": 123 }String: JSON strings are written in double quotes. For example:
{ "empname": "Twinkle" }Boolean: The value may be true or false . For example:
{ "Pass":true }Object: A JSON object can be any set of pairs of values. For example:
{"Employee": { "name":"Twinkle", "empid":1234, "position":"Trainer", "city":"London" }}Array: - the values can be grouped in an array. For example:
{"Employee": [ "name":"Twinkle", "empid":1234, "position":"Trainer", "city":"London" ]}Null: These are empty or no values. For example:
{ "value":null }
The syntax of JSON objects is
var Employee = { "name":"Twinkle", "empid":1234, "position":"Trainer", "city":"London" }As previously mentioned, the JSON objects are within curly brackets, {}, and contain key-value pairs that are separated by a colon (:). The key in the case of objects is also always a string that is within double quotes. The values pertaining to these keys may be of any data types (such as number, string, array, and so on).
There are two ways to access the object values: using dot (.) notation, like Employee.name , or by placing the value in brackets, like Employee["name"] .
There are three ways to create JSON objects via JS coding:
Create an empty object:
var myEm = {};Create a new object:
var myEm = new Object();Create a JSON object with key/value pairs:
var myEm = { "name":"Twinkle", "empid":1234, "position":"Trainer", "city":"London" }
Listing shows a fully working example.
var product, val;product = { "prname":"Smart Phone", "price":20000, "company":"Sony", "camera":null };console.log( "Product name is: " + product["prname"] + " company: " + product["company"] );This code is the same as code shown in Listing .
The values are in the form of array as in JavaScript. The values are held in square brackets, [], and array values can be of any data types (number, string, array, object, Boolean, or null).
{"soldin" : [ "US", "UK" ]}To access array values, use an index number like this:
soldin[1];To better understand this concept, consider Listing .
var sellingitem;sellingitem = {"itemname":"Smart Phone","itemprice":20000,"soldin":[ "US","UK" ]};console.log( "Product " + sellingitem.itemname +" is sold in " + sellingitem.soldin[0] + ' and ' +sellingitem.soldin[1] );This example has a variable sellingitem that represents an object, with suitable values assigned to it. Within this object is an array soldin that contains the countries in which the item is sold. The console.log method is used to print the product name and the countries in the console. The output of Listing .
In this case, weve defined a JSON array for a key value company with different attributes like Sony, Apple, Lenovo, and Samsung. Now, to access this array value, we use an index number with an object. So in this way we can identify a product brand name from a JSON array.
The parse method allows you to convert a data stream received in the form of a string (i.e., information in JSON form) into a JS object. To better understand the usage of the method, consider a scenario where you have a string containing name , ID , position, and trainer data pertaining to an employee. The parse method will use this as follows:
var Employee = JSON.parse('{ "name":"Twinkle", "empid":1234, "position":"Trainer", "city":"London" }');The parse method will take as input the entire JSON represented in string form. The result of this method execution will be returned in the form of an employee object.
The complete code for this example is shown in Listing .
var Employee;Employee = JSON.parse('{ "name":"Twinkle", "empid":1234, "position":"Trainer", "city":"London" }');Font size:
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