Introducing JavaScript. Server-Side and Client-Side Programming Server-side programming –Program placed on server that hosts Web site –Program then used.

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    01-Apr-2015

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Introducing JavaScript Slide 2 Server-Side and Client-Side Programming Server-side programming Program placed on server that hosts Web site Program then used to modify contents and structure of Web pages Slide 3 Server-Side and Client-Side Programming Client-side programming Runs programs on users computer Programs likely to be more responsive to users complement server-side programming Slide 4 Server-Side Programming Slide 5 Client-Side Programming Slide 6 Combining Client-Side and Server-Side Programming Slide 7 Introducing JavaScript Server-side Programs pose problems Client-side Programs were developed to run programs and scripts on the client side of a Web browser Slide 8 The Development of JavaScript Java Developed by Sun Microsystems Programs designed to be run within Java interpreters An example of a compiled language JavaScript Developed by NETSCAPE, An interpreted language Internet Explorer supports a version called JScript Slide 9 Comparing Java and JavaScript Slide 10 Versions of JavaScript Slide 11 The Development of JavaScript Jscript is a version of JavaScript supported by Internet Explorer The European Computer Manufacturers Association (ECMA) develops scripting standards The standard is called ECMAScript but browsers still generally call is JavaScript Slide 12 Inserting JavaScript into a Web Page File Outline the main tasks you want the program to perform first A JavaScript program can either be placed directly in a Web page file or saved in an external text file Slide 13 Inserting JavaScript into a Web Page File Insert a client-side script in a Web page when using the script element Comments are useful for hiding scripts from older browsers Specify alternative content using the nonscript element for browsers that dont support scripts (or have their script support disabled) Slide 14 Writing Output to the Web Page An object-based programming language writes the output by manipulating tasks An action you perform on an object is called a method Slide 15 Writing Output to the Web Page To write text to a Web page, use the following JavaScript commands: document.write(text); or document.writeln(text) Where text is the content to be written to the page. The doucment.write() and document.writeln() methods are identical, except that the document.writeln() method preserves any line breaks in the text string. Slide 16 Working with the Script Element Script element Used to enter scripts into an HTML or XHTML file Syntax script commands Slide 17 Writing Output to a Web Document Inserting amir.minai@northampton.ac.uk in a Web documentamir.minai@northampton.ac.uk document.write(amir.minai@northampton.ac.uk"); Slide 18 The document.write() Method One way to send output to the Web document Object Can be any item, including mouse pointer or window scrollbars Method Process by which JavaScript manipulates the features of an object Slide 19 Understanding JavaScript Rules and the Use of White Space JavaScript Is case sensitive Ignores most occurrences of extra white space Line breaks occurring within a statement can cause error Good practice to not break a statement into several lines Slide 20 Supporting Non-JavaScript Browsers noscript element Used by browsers that do not support scripts Syntax alternative content Slide 21 Working with Variables Variable A named item in a program that stores information Used to represent values and text strings Values can change as the program runs Slide 22 Working with Variables and Data JavaScript variable types: Numeric variables String variables Boolean variables Null variables You declare a variable before using it Slide 23 Working with Variables and Data Numeric variable- any number, such as 13, 22.5, etc Can also be expressed in scientific notation String variable- any group of text characters, such as Hello or Happy Holidays! Must be enclosed within either double or single quotations (but not both) Boolean variable- accepts only true and false values Null variable- has no value at all Slide 24 Declaring a Variable Tells JavaScript interpreter to reserve memory space for the variable Statement to declare a variable var variable; Declaring three variables var emLink, userName, emServer; Slide 25 Declaring a JavaScript Variable You can declare variables with any of the following JavaScript commands: var variable; var variable = value; variable = value; Where variable is the name of the variable and value is the initial value of the variable. The first command creates the variable without assigning it a value; the second and third commands both create the variable and assign it a value. Slide 26 Declaring a Variable Limits on variable names First character must be either a letter or an underscore character ( _ ) Remaining characters can be letters, numbers, or underscore characters Variable names cannot contain spaces Reserved words cannot be used Slide 27 Writing a Variable Value to a Web Document Variable Can be used in place of value it contains Writing a text string to a Web page var libName = Duston Public Library"; document.write(libName); Plus symbol ( + ) Can be used to combine variable with text string Slide 28 Working with Dates Create a date object to store date information Date Methods Slide 29 Working with Expressions and Operators Expressions are JavaScript commands that assign values and variables Operators are elements that perform actions within expressions Arithmetic operators: perform simple mathematical calculations Binary operators: work on two elements in an expression Unary operators: work on only one variable Increment operators: can be used to increase the value of a variable by 1 Assignment operators: used to assign values in expressions Slide 30 Working with Expressions and Operators The Math object is a JavaScript object used for calculations other than simple math Slide 31 Creating a Function to Perform an Action Functions Collection of commands that perform an action or return a value Include a function name Include a set of commands that run when function is called Some require parameters Slide 32 Creating a Function to Perform an Action Syntax of a JavaScript function function function_name(parameters){ JavaScript commands } Calling a function function_name(parameter values) Slide 33 Functions and Variable Scope Variable scope Indicates where and how the variable can be used in your application Can be local or global Slide 34 Functions and Variable Scope Local scope Variable created within a JavaScript function Global scope Variables not declared within functions Slide 35 Creating a Function to Return a Value For a function to return a value It must include a return statement Syntax of a function that returns a value function function_name(parameters) { JavaScript commands return value; } Slide 36 Commenting JavaScript Code Comments Explain what your programs are designed to do and how they work Multiline comment /* The showEM() function displays a link to the users e- mail address. The username and e-mail server name are entered in reverse order */ Slide 37

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