java barcode Note that in assigning the predefined function, we omit the parentheses. If we were to write in Java

Draw Denso QR Bar Code in Java Note that in assigning the predefined function, we omit the parentheses. If we were to write

Note that in assigning the predefined function, we omit the parentheses. If we were to write
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myObject.sayHello=sayHello();
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then we would execute the sayHello function and assign the return value, in this case null, to the sayHello property of myObject. We can attach objects to other objects in order to build up complex data models and so on:
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var myLibrary=new Object(); myLibrary.books=new Array(); myLibrary.books[0]=new Object(); myLibrary.books[0].title="Turnip Cultivation through the Ages"; myLibrary.books[0].authors=new Array(); var jim=new Object(); jim.name="Jim Brown"; jim.age=9; myLibrary.books[0].authors[0]=jim;
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This can quickly become tedious (often the case where turnips are involved, I m afraid), and JavaScript offers a compact notation that we can use to assemble object graphs more quickly, known as JSON. Let s have a look at it now. Using JSON The JavaScript Object Notation (JSON) is a core feature of the language. It provides a concise mechanism for creating arrays and object graphs. In order to understand JSON, we need to know how JavaScript arrays work, so let s cover the basics of them first. JavaScript has a built-in Array class that can be instantiated using the new keyword:
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myLibrary.books=new Array();
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APPENDIX B
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JavaScript for object-oriented programmers
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Arrays can have values assigned to them by number, much like a conventional C or Java array:
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myLibrary.books[4]=somePredefinedBook;
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Or they can be associated with a key value, like a Java Map or Python Dictionary, or, indeed, any JavaScript Object:
myLibrary.books["BestSeller"]=somePredefinedBook;
This syntax is good for fine-tuning, but building a large array or object in the first place can be tedious. The shorthand for creating a numerically indexed array is to use square braces, with the entries being written as a comma-separated list of values, thus:
myLibrary.books=[predefinedBook1,predefinedBook2,predefinedBook3];
And to build a JavaScript Object, we use curly braces, with each value written as a key:value pair:
myLibrary.books={ bestSeller : predefinedBook1, cookbook : predefinedBook2, spaceFiller : predefinedBook3 };
In both notations, extra white space is ignored, allowing us to pretty-print for clarity. Keys can also have spaces in them, and can be quoted in the JSON notation, for example:
"Best Seller" : predefinedBook1,
We can nest JSON notations to create one-line definitions of complex object hierarchies (albeit rather a long line):
var myLibrary={ location : "my house", keywords : [ "root vegetables", "turnip", "tedium" ], books: [ { title : "Turnip Cultivation through the Ages", authors : [ { name: "Jim Brown", age: 9 }, { name: "Dick Turnip", age: 312 } ], publicationDate : "long ago" }, { title : "Turnip Cultivation through the Ages, vol. 2",
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authors : [ { name: "Jim Brown", age: 35 } ], publicationDate : new Date(1605,11,05) } ] };
I have assigned three properties to the myLibrary object here: location is a simple string, keywords is a numerical list of strings, and books a numerically indexed list of objects, each with a title (a string), a publication date (a JavaScript Date object in one case and a string in the other), and a list of authors (an array). Each author is represented by a name and age parameter. JSON has provided us with a concise mechanism for creating this information in a single pass, something that would otherwise have taken many lines of code (and greater bandwidth). Sharp-eyed readers will have noted that we populated the publication date for the second book using a JavaScript Date object. In assigning the value we can use any JavaScript code, in fact, even a function that we defined ourselves:
function gunpowderPlot(){ return new Date(1605,11,05); } var volNum=2; var turnipVol2={ title : "Turnip Cultivation through the Ages, vol. " +volNum, authors : [ { name: "Jim Brown", age: 35 } ], publicationDate : gunpowderPlot() } ] };
Here the title of the book is calculated dynamically by an inline expression, and the publicationDate is set to the return value from a predefined function. In the previous example, we defined a function gunpowderPlot() that was evaluated at the time the object was created. We can also define member functions for our JSON-invoked objects, which can be invoked later by the object:
var turnipVol2={ title : "Turnip Cultivation through the Ages, vol. "+volNum, authors : [ { name: "Jim Brown", age: 35 } ],
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