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Javascript and Basic Programming Concepts

Javascript and Basic Programming Concepts. What is a Program?. A program is a specific set of instructions written in a computer language to perform a specified task. Usually comes in an Application file or “.exe”. What are some programming Languages?.

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Javascript and Basic Programming Concepts

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  1. Javascript and Basic Programming Concepts

  2. What is a Program? • A program is a specific set of instructions written in a computer language to perform a specified task. • Usually comes in an Application file or “.exe”

  3. What are some programming Languages? • Python, Java, C, C++, Fortran- General Programming • HTML, XML, LaTeX, XHTML- Markup languages • CSS – style sheet language • SQL, Oracle, MySQL – Database • Mathematical, Matlab, Maple – Math • Machine Language

  4. How do we program? • Have to use a programming language • Programming Language: an artificial language designed to communicate instructions to a machine (computer)

  5. How Do You Give Directions? • Lots of details? • Specific steps? • Just the gist? • What language?

  6. Giving Directions With JavaScript • Just one way of talking to a computer. • Not related to Java • Useful for games and widgets • Useful for websites

  7. Just the Basics • Format • Output • Variables • Functions • Input • Conditionals

  8. Format • Goes in head or body or another tag or another file • Uses <script> </script> tags • Need to specify the language in the <script> tag • <script type=“text/javascript”> </script>

  9. Output • Statements that tell the computer to print something somewhere. • document.write(WhateverYouWantToPrint)

  10. Output Example <html> <head> <title>First JavaScript page</title> </head> <body> <script type="text/javascript"> document.write("<h1>Hello World</h1>"); </script> </body> </html>

  11. Resulting Webpage

  12. Hello Part 2 <html> <head> <title>First JavaScript page</title> </head> <body> <script type="text/javascript"> document.write("<h1>Hello World</h1>"); document.write("<h2>Or Whoever Is Listening</h2>"); </script> </body> </html>

  13. And the Webpage

  14. Why Use JavaScript? What if we wanted to calculate 2*3? <html> <body> 2*3=2*3 </body> </html>

  15. And the Resulting Webpage

  16. JavaScript Solution <html> <head> <title>First JavaScript page</title> </head> <body> <script type="text/javascript"> answer = 2*3; document.write("2*3="+ answer); </script> </body> </html>

  17. Resulting JavaScript Webpage

  18. Variables • A variable is a letter, word, or phrase that contains information • Example: x = 5

  19. Variable Data types • Integers – whole numbers (1, -8, 563) • Floating Point (float, double) – decimal (3.14, -5.555) • Complex – imaginary numbers (3 + 2i) • String – words, sentences, phrases (“Hello there.”) • Char – one character or letter (‘a’, ‘b’, ‘c’) • Boolean – True or False

  20. Another Calculating Example <html> <head> <title>First JavaScript page</title> </head> <body> <script type="text/javascript"> timesanswer = 2*3; plusanswer = 2+3; document.write("2*3="+ timesanswer + " and 2+3=" + plusanswer); </script> </body> </html>

  21. Along With the Webpage

  22. What if We Want Three Calculations? <html> <head> <title>First JavaScript page</title> </head> <body> <script type="text/javascript"> answer = 2*3; document.write("2*3="+ answer + "<br><br>"); answer = 10*5; document.write("10*5="+ answer + "<br><br>"); answer = 1024*4; document.write("1024*4="+ answer + "<br><br>"); </script> </body> </html>

  23. What if 100’s of Calculations? • Or lots of something else beside calculations? • Functions are an answer! • Functions can go in the head and be called from the body.

  24. Example Using a Function to Calculate <html> <head> <title>First JavaScript page</title> <script type="text/javascript"> function calculateAnswers(number1,number2){ timesanswer = number1*number2; document.write(number1 + "*" + number2 + "=" + timesanswer); document.write("<br><br>"); } </script> </head> <body> <script type="text/javascript"> calculateAnswers(2,3); calculateAnswers(10,5); calculateAnswers(1024,4); </script> </body> </html>

  25. First Function Webpage

  26. Not Much Fun Without User Input • Can use <form> </form> tags • Inside the form tags use <input> tag • Some types of input • Text • Button • Checkbox • Types have attributes such as size and name • Can respond back to the user with an Alert (tiny popup window)

  27. Sample User Input Page <html> <head> <title>First JavaScript page</title> <script type="text/javascript"> function calculateAnswers(number1,number2){ timesanswer = number1*number2; alert("The answer is: " + timesanswer); } </script> </head> <body> Enter two numbers to be multiplied: <form> <p><b>Number1:</b> <input type="TEXT" size="10" name="num1"> <p><b>Number2:</b> <input type="TEXT" size="10" name="num2"> <p><input type="BUTTON" value="Calculate Answer" onClick="calculateAnswers(num1.value, num2.value);"</p> </form> </body> </html>

  28. Resulting Webpage • Check it out at http://www.cs.mtsu.edu/~pettey/1150/form.html

  29. What About Conditions? • If something happens, do something, otherwise do something else... • That is the computer can do different things based on some decision.

  30. Try Out and Example Without Decision Making • The following website does division of two numbers. Try it out. Be sure to try and divide by 0. • http://www.cs.mtsu.edu/~pettey/1150/form2.html

  31. How to do a JavaScript Decision If (something happens){ take some action } else{ take a different action }

  32. Something Happens?

  33. Example With Decision Making • Check out http://www.cs.mtsu.edu/~pettey/1150/form3.html • Be sure to view the page source to see the condition.

  34. More Examples • Calculate the average of three test scores http://www.cs.mtsu.edu/~pettey/1150/form4.html • Read info and send email if over 18 http://www.cs.mtsu.edu/~pettey/1150/email.html • Vote with alert after each button click http://www.cs.mtsu.edu/~pettey/1150/vote.html • Vote with alert only after announce the winner button is clicked http://www.cs.mtsu.edu/~pettey/1150/vote2.html

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