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JavaScript Missing Manual, Ch. 2
This document discusses key concepts in JavaScript including statements, commands, data types, variables, operators, and arrays. It covers declaring and assigning variables, built-in data types like numbers and strings, basic math operators, and using arrays to store and manipulate data. The document also introduces comments and provides examples of JavaScript code.
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JavaScript Missing Manual, Ch. 2
- 1. JavaScript: The MissingManual Chapter 2: The Grammar of JavaScript Author: David S. McFarland | Publisher: O’Reilly Copyright 2010
- 2. Statements JavaScript statement:a basic programming unit, usually representing a single step in a JavaScript program combine statements to create a JavaScript program each statement ends with a semicolon like a period at the end of a sentence Copyright 2010
- 3. Commands Commands areusually called functions or methods like verbs in a sentence, commands get things done Examples: alert(); document.write(); Chapter 3 will focus on functions . Copyright 2010
- 4. Types of DataIn JavaScript the three most common types of data are: numbers strings Boolean Copyright 2010
- 5. Numbers a number is used for counting or calculating Example: document.write(5 + 15) Result: 20 is written to the page Copyright 2010
- 6. Strings A string is simply a series of letters and other symbols enclosed inside of quote marks you can use either single or double quotes ‘ Welcome back!’ “ Welcome back!” Copyright 2010
- 7. Booleans A Boolean value is either true or false typically used to make decisions Example: The visitor filled in the “name” textbox . . . true or false? Copyright 2010
- 8. Variables A variable is a way to store information so that you can use and manipulate it variables hold information that can vary Think of a variable as a container or basket the container remains the same even if you change the contents of the container Copyright 2010
- 9. Creating a VariableTwo-step process: declare the variable name the variable Example: var score; Copyright 2010
- 10. Creating a VariableRules: A variable name . . . must begin with a letter, $, or _ can only contain letters, numbers, $, and _ is case sensitive must not be the same as a keyword (reserved words) Google “JavaScript keywords” Copyright 2010
- 11. Using Variables Oncea variable is created you can store any type of data that you’d like in it var score; var name_first; score = 0; name_first = “Peter”; Copyright 2010
- 12. Using Variables Oncea variable is created you can store any type of data that you’d like in it var score; score = 0; var score = 0; Copyright 2010 assignment operator
- 13. Data Types &Variables Operator – a symbol or word that can change one or more values into something else used to modify data Copyright 2010
- 14. Basic Math MathOperators: Copyright 2010 Result Example Operator 3 15 / 5 / 50 5 * 10 * 20 25 - 5 - 30 5 + 25 +
- 15. Order of OperationsSome operations take precedence over others . . . Multiplication (*) and division (/) takes precedence over addition (+) and subtraction (-) Copyright 2010
- 16. Order of OperationsUse parentheses to group operations Example: 4 + 5 * 10 result: 54 (4 + 5) * 10 result: 90 Copyright 2010
- 17. Combining Strings Concatenation – combining strings by using the + operator var name_first = “Peter”; var name_last = “Kery”; var full_name = name_first + name_last; Copyright 2010
- 18. Combining Numbers & Strings Copyright 2010
- 19. Changing the Valuesin Variables Example: var score = 0; score = score + 100; Copyright 2010
- 20. Shortcuts for Performing Math Copyright 2010 score = score + 1; score ++; ++ score = score / 10; score /= 10; /= score = score * 10; score *= 10; *= score = score - 1; score --; -- score = score - 10; score -= 10; -= score = score + 10; score += 10; += Alternate Example Operator
- 21. Tutorial #1 Usingvariables to create messages: open file 2.1.html add a <script> element create two variables for first and last name add three document.write statements to print out the full name in a paragraph 2.1.html Copyright 2010
- 22. Tutorial #2 Askingfor information: open file 2.2.html add a prompt() command to first script: var name = prompt(“What is your ► name?”, “”); 2.2.html Copyright 2010
- 23. Tutorial #2 Askingfor information (continued): add a document.write statement to second script: document.write(“<p>Welcome” + ► name + “</p>” ); 2.2.html Copyright 2010
- 24.
- 25. Creating an ArrayCopyright 2010
- 26. Assessing Items inan Array Copyright 2010
- 27. Adding Items toan Array Copyright 2010
- 28. Deleting Items froman Array Copyright 2010
- 29. Adding & Deletingwith splice() Copyright 2010
- 30. Tutorial #3 Writingto a Web page using arrays 2.3.html Copyright 2010
- 31. Comments A comment is simply a line or more of notes interpreter ignores comments useful reminders for how the script works Copyright 2010
- 32. Comments Styles: //This is a comment. /* This is also a comment that covers multiple lines */ Copyright 2010
- 33. Comments Examples: //create a variable for first name. var name_first; // remember no SINs /* The purpose of this script is to capture the visitors name and print it back to the page. */ Copyright 2010
- 34. JavaScript blah, blah,blah . . . Copyright 2010