JavaScript Missing Manual, Ch. 2
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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.
JavaScript Missing Manual, Ch. 2
- 1. JavaScript: The Missing Manual 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 are usually 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 Data In 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 Variable Two-step process: declare the variable name the variable Example: var score; Copyright 2010
- 10. Creating a Variable Rules: 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 Once a 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 Once a 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 Math Operators: Copyright 2010 Result Example Operator 3 15 / 5 / 50 5 * 10 * 20 25 - 5 - 30 5 + 25 +
- 15. Order of Operations Some operations take precedence over others . . . Multiplication (*) and division (/) takes precedence over addition (+) and subtraction (-) Copyright 2010
- 16. Order of Operations Use 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 Values in 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 Using variables 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 Asking for 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 Asking for information (continued): add a document.write statement to second script: document.write(“<p>Welcome” + ► name + “</p>” ); 2.2.html Copyright 2010
- 25. Creating an Array Copyright 2010
- 26. Assessing Items in an Array Copyright 2010
- 27. Adding Items to an Array Copyright 2010
- 28. Deleting Items from an Array Copyright 2010
- 29. Adding & Deleting with splice() Copyright 2010
- 30. Tutorial #3 Writing to 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