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Modern JavaScript Develop And Design Instructor’s Notes Chapter 6 - Complex Variable Types Modern JavaScript Design And Develop Copyright © 2012 by Larry.

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Presentation on theme: "Modern JavaScript Develop And Design Instructor’s Notes Chapter 6 - Complex Variable Types Modern JavaScript Design And Develop Copyright © 2012 by Larry."— Presentation transcript:

1 Modern JavaScript Develop And Design Instructor’s Notes Chapter 6 - Complex Variable Types Modern JavaScript Design And Develop Copyright © 2012 by Larry Ullman

2 Objectives Use the Date object Create a Date object representing a specific date and time using three different approaches Invoke Date methods to fetch parts of a represented date and time Invoke Date methods to fetch the date and time in different formats

3 More Objectives Work with different time zones Change the represented date and/or time Perform date arithmetic Create arrays Access individual array elements

4 More Objectives Invoke array methods for adding and removing elements Convert between arrays and strings Create objects Create objects with properties Access object properties

5 The Date Object Able to represent any date and time 100 million days before or after the epoch Epoch = Midnight on January 1, 1970 var today = new Date();

6 Creating Specific Dates var someday = new Date(milliseconds); var someday = new Date(year, month, day, hour, minute, second, milliseconds); var someday = new Date('date string');

7 Using Atomic Values var thatDate = new Date(2012, 6, 5); // July is 6, not 7! var thatDate = new Date(2012, 6, 5, 13, 30); // July is 6, not 7!

8 Using Timestamps // 10 days after the epoch: var thatDate = new Date( * 10);

9 Using a String July 5, 2012 Jul 5, July /05/ /05/ :30 Thu, 05 Jul :30:00 GMT-0500

10 Date Methods MethodReturns getDate()Day of the month getDay()Day of the week, with 0 = Sunday getFullYear()Year as four digits getHours()Hours, from 0 to 23 getMilliseconds()Milliseconds getMinutes()Minutes getMonth()Month number, with 0 = January getSeconds()Seconds getTime()Milliseconds from the epoch

11 More Date Methods MethodExample toDateString() Thu Jul toISOString() T17:30:05.000Z toJSON() T17:30:05.000Z toLocaleDateString()July 5, 2012 toLocaleString()July 5, :30:05 PM EDT toLocaleTimeString()1:30:05 PM EDT toString()Sun Aug :30:05 GMT-0400 (EDT) toTimeString()13:30:00 GMT-0400 (EDT)

12 Working with Time Zones Set dates using timestamps or strings. Fetch local date and time using any method. Or, use getTimeZoneOffset() and do the math.

13 Changing Dates MethodSets setDate()Day of the month setFullYear()Year setHours()Hours setMilliseconds()Milliseconds setMinutes()Minutes setMonth()Month (staring at 0 for January) setSeconds()Seconds setTime()Date and time (using a timestamp)

14 Date Arithmetic Perform math using timestamps Use setX() and getX() Subtract one Date object from another to calculate the interval

15 Arrays

16 Creating Arrays var myVar = new Array(); var myList = new Array(1, 2, 3); var people = new Array('Fred', 'Daphne', 'Velma', 'Shaggy'); var options = new Array(true, false); var myVar = []; var myList = [1, 2, 3]; var people = ['Fred', 'Daphne', 'Velma', 'Shaggy']; var collection = [1, 'Fred', 'Daphne', 2, false];

17 Accessing Elements var people = ['Fred', 'Daphne', 'Velma', 'Shaggy']; people.length; // 4 people[0]; // Fred

18 Array Indexes var people = ['Fred', 'Daphne', 'Velma', 'Shaggy']; people[4] = 'Charlie'; people[0] = 'Mac'; // People now stores 'Mac', 'Daphne', 'Velma', 'Shaggy', 'Charlie' people.length; // 5 people[10] = 'Dennis'; people.length; // 11! people[people.length] = 'Dee';

19 Accessing All Elements for (var i = 0; i < myList.length; i++) { // Do something with myList[i]. } for (var i = 0, count = myList.length; i < count; i++) { // Do something with myList[i]. } for (var i = 0, count = myList.length; i < count; i++) { if (myList[i] !== undefined) { // Do something with myList[i]. }

20 Adding Elements var primes = []; primes.push(1); // [1] primes.push(3, 5, 7); // [1, 3, 5, 7] var primes = [3, 5, 7]; // [3, 5, 7] primes.unshift(1); // [1, 3, 5, 7] var primes = []; primes.concat(1, [3, 5, 7]); // [1, 3, 5, 7]

21 Removing Elements var primes = [1, 3, 5, 7]; // [1, 3, 5, 7] primes.pop(); // [1, 3, 5] var primes = [3, 5, 7]; // [3, 5, 7] primes.shift(); // [5, 7]

22 Arrays  Strings var gang = 'Fred,Daphne,Velma,Shaggy'; var people = gang.split(',');

23 Objects

24 Creating Objects var myObj = new Object();s var myObj = {};

25 Creating Properties var me = { name: 'Larry Ullman', age: 42, car: { make: 'Honda', model: 'Fit', year: 2008 }, favoriteColors: ['Black', 'Blue', 'Gray'], tired: true }; var chapter = {num: 6, title: 'Complex Data Types'};

26 Accessing Properties var chapter = { num: 6, title: 'Complex Data Types' }; chapter.num; // 6

27 Accessing All Properties for (var p in myObj) { // Use myObj[p]. }

28 Arrays vs. Objects Always use a simple type, if you can. Use Date when using dates and times. Use arrays when: –The order of the stored values is important. –The values can be numerically indexed. –You may need to quickly know how many values are stored. For all other complex data, use objects.


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