JavaScript Lesson 1 TBE 540

Prerequisites  Before beginning this lesson, the learner must be able to… Create a basic web page using a text editor and/or a web page editor. Edit the existing HTML code of a web page.

Objectives  The learner will be able to successfully add JavaScript code to a web page.  The JavaScript will produce a useful effect and enhance the page’s value to the user.

What is JavaScript?  JavaScript is a programming language. This means that the instructions you write in JavaScript will make something happen.  You can include it easily within the HTML code of a web page to customize the page.

What is JavaScript? JavaScript is related to Java and C++, but it does not need to be “compiled” (translated to binary) before it is used. JavaScript is not the same as Java.

What is JavaScript? JavaScript code is “interpreted” - the browser executes each line of code as it is encountered. JavaScript is free and many existing samples are available. (see TBE 540 HTML page for links)

What can you do with JavaScript?  Visit the links from Lesson 8 on the TBE 540 HTML page to see what can be done using JavaScript. ( 0/lesson8.html) 0/lesson8.html

 Would any of these JavaScript samples be appropriate for your web project?  Later you will learn how to add JavaScript code to your pages. What can you do with JavaScript?

How do you add JavaScript to a web page?  If you are going to add JavaScript, it is necessary to be able to edit the HTML code of a web.  If you are using a web editor and are unsure of how to edit HTML code, check HELP in your editor.

How do you add JavaScript to a web page?  At first (maybe always) you will be simply pasting in JavaScript code copied from other sources.  Sometimes you will customize the code.  You can also type the code into your HTML.

How do you add JavaScript to a web page?  When you copy or type the code, notice where it should go.  JavaScript is most commonly placed in the section of a page, but there are often parts that must go elsewhere.

JavaScript - Sample  Here is an explanation of a simple use of JavaScript - asking a question and displaying an answer.  You will try this in the Fun with Buttons! exercise.

 In this case, there will be a JavaScript function (small program) called getName() placed in the HEAD section of the HTML.  It will ask for a name and print Hi and the name. JavaScript - Sample

 Here’s what the function looks like (explanations follow): var stName="XX" function getName() { stName=prompt("Please enter your name"," ") alert("Hi, " + stName) } JavaScript - Sample

 The script tags are needed to identify this code as JavaScript. var stName="XX" function getName() { stName=prompt("Please enter your name"," ") alert("Hi, " + stName) } JavaScript - Sample

 The line beginning var sets up a variable called stName with a beginning value of XX (just to fill it up). var stName="XX" function getName () { stName=prompt("Please enter your name"," ") alert("Hi, " + stName) } JavaScript - Sample

 function getName() defines the name of the function (notice the two parentheses). var stName="XX" function getName() { stName=prompt("Please enter your name"," ") alert("Hi, " + stName) } JavaScript - Sample

 The braces { } show where the function begins and ends. var stName="XX" function getName() { stName=prompt("Please enter your name"," ") alert("Hi, " + stName) } JavaScript - Sample

 The line beginning stName= displays the message Please enter your name and waits for an entry, which will become the value of stName. var stName="XX" function getName() { stName=prompt("Please enter your name"," ") alert("Hi, " + stName) } JavaScript - Sample

 The line beginning alert displays Hi, and the value of the variable stName. var stName="XX" function getName( ) { stName=prompt("Please enter your name"," ") alert("Hi, " + stName) } JavaScript - Sample

 Something has to start the getName() function.  In the Fun with Buttons! exercise, it will be clicking on a graphic or a “form” button (more about forms in a later lesson).

JavaScript - Sample  To start a function, its name will be somewhere in the HTML: getName()  You will see this code in an IMG tag: onclick=“getName()”  When the graphic is clicked, the function starts.

JavaScript - Sample  You will also see this code between and tags :  FORMs are used to make buttons and input boxes appear on a web page.

Self Check - JS Lesson 1  True or false - JavaScript and Java are exactly the same thing.

Self Check - JS Lesson 1  True or false - JavaScript and Java are exactly the same thing.  False - Java must be “complied” (translated to binary) before running, while JavaScript runs automatically every time the web page is opened. Java is also much more powerful than JavaScript.

Self Check - JS Lesson 1  JavaScript is most often found in the _____ section of the HTML code for a web page.

Self Check - JS Lesson 1  JavaScript is most often found in the _____ section of the HTML code for a web page. {may be here, too}

Self Check - JS Lesson 1  Which of the following is the correct way to begin JavaScript?

Self Check - JS Lesson 1  Which of the following is the correct way to begin JavaScript? * * {upper and lower case must be exact}

Self Check - JS Lesson 1  Suppose you created a function called HAPPY(). What command would activate the function?  happy()  HAPPY  HAPPY()

Self Check - JS Lesson 1  Suppose you created a function called HAPPY(). What command would activate the function?  happy()  HAPPY  HAPPY() The name must be exactly the same, including upper and lower case. The parentheses must be included.

Self Check - JS Lesson 1  Which of the following commands waits for input? prompt alert

Self Check - JS Lesson 1  Which of the following commands waits for input? prompt {waits for input and Return/Enter} alert {displays message only}

Try some!  Complete the Fun with Buttons! exercise.  Go find some interesting JavaScript code and try it out.  The samples on the TBE 540 HTML page are a good place to start.