Introduction

 The scripting language most often used for client-side web development.  Influenced by many programming languages, easier for nonprogrammers to work with.  Best known for its use in website development.  Unrelated to Java programming -- although both have a common C syntax  Supports all the structured programming syntax in C, Java, C#. – variables, conditionals, repetition structures, data structures, classes

 Primary use is to write function that are embedded in HTML pages:  Examples:  popping up a new window with control over size, position, attributes.  Validation of web form input values to make sure they are acceptable before submitting to server.  Changing images as a mouse moves over them.  The JavaScript interpreter interprets JavaScript source code and execute the script accordingly.  not a compiled language like C or C++  Most common host environment for JavaScript is a web browser

 JavaScript is object based  Client side scripting – runs on browser, not on server  Don't need to send and retrieve data to the server  Saves time  Does not need to be compiled  Script interpretation done by browser

 To tell html you will be using JavaScript do this: ….  Everything between the opening and closing tags is JavaScript  Browser treats code as scripting language not html  Place inside head tag, the browser interprets first so the JavaScript will execute before the body

 If placed in tag, it gets run first  If placed in tag, runs in order it was placed  JavaScript can be placed in an external file  External JavaScript files end with.js extension

document.write(“hello world!"); alert(‘hello world’);  “hello world” is a character string - a string of characters contained between double or single quotes  parentheses following the name of the method containing the arguments that the method requires to perform its task.  Every statement should end with a semicolon (not required but a programming standard).  JavaScript is case sensitive  method write() – write a line of text

 Good practice to comment your code – explain what your code does  Comments – ignored by the browser  One line comment // This is a one line comment  Multi-line comment /* this is a multi-line comment I have a lot to explain */

 In Chrome – JavaScript Debugger is F12 or CTRL, shift J  In Firefox, use the error console (CTRL, Shift, J)  Provides clear description of errors  Identifies the line in your code where error occurred

 Fade in practice  chapter1 – 1.html