1. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 1 http://www.cs.cityu.edu.hk/~helena JavaScript Global Functions and Objects I Introduction to JavaScript Objects and HTML Element Objects Global Functions: isFinite, isNaN, escape/unescape, eval Creation of Objects: the new operator and constructor functions Commonly used objects: Window: Math and Random Number Generation Date ------------------------------------------------------------------------------ In next powerpoint, we will have: Array String Document and Adding Cookies Forms: Style, Cascading Style Sheets (CSS) and Dynamic HTML (DHTML)

2. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 2 http://www.cs.cityu.edu.hk/~helena What are Objects Objects : An object is a collection of named values called properties. Each property may contain any type of data, functions, and even other objects. Example:The document object may contain a form object named F1: document.F1 The form may contain 2 input box objects with names equal to n1 and n2: document.F1.n1 and document.F1.n2 The input boxes may contain several properties like: value, size, readOnly: document.F1.n1.value The properties can be examined as follows: [Refer to Lec03_Slide12_V4_MarksToGrade.htm]

3. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 3 http://www.cs.cityu.edu.hk/~helena What are Objects Exercise: [Refer to Lec02_Slide13_V4_MarksToGrade.htm] What will be shown by running the statements below? javascript:alert(document.F1.CGrade.readOnly) javascript:alert(document.F1.CGrade) javascript:alert(document.F1) javascript:alert(document) javascript:alert(document.write) javascript:alert(convertAll)

4. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 4 http://www.cs.cityu.edu.hk/~helena HTML Elements as JavaScript Objects Handling HTML Elements as JavaScript Objects Contents in a webpage are automatically represented as "objects contained in the document object" (ie. a property of the document object). 2 simple methods to refer to these contents: (1)Each element object in the webpage body, that contains an ID, can be referred using document.getElementById(id). If it contains a pair of starting and ending tags, the HTML text in-between the tags can be referred as the innerHTML property: document.getElementById(id).innerHTML (2)For forms and form elements, there is one more method to refer to them. Any form object is an individual property of the document, can be referred by its name. document.formname Each element in the form is an individual property of the form, can be referred by its name. document.formname.elementname The set of properties defined for one kind of object is usually different from others. For example, an input box contains the value property but an image does not. The list of properties for each kind of object can be found in the appendix of many JavaScript books or on-line resources. However, practically we use only a few of them.

5. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 5 http://www.cs.cityu.edu.hk/~helena What are Objects A function stored as an object property is often called a method. eg. document.write( ); All JavaScript code loaded in a browser window is contained in a global object: window The window object contains - all global functions (functions that not really specific to the "window"): eg. parseInt( ) - many useful window methods, eg. window.setInterval( ), window.alert().. - the document object - other useful window properties, eg. window.status (the text shown in the status bar) To access window properties, like window.document and window.setInterval( ), we may omit the window. part, ie. simply document, setInterval(..) Some people prefer to keep the window. part : easier to understand the code (to know that 'the property belongs to the window object'). The Global functions do not relate much to the browser window, we prefer to type their names directly like parseInt, instead of window.parseInt. Some common Global functions: parseFloat, parseInt isFinite, isNaN, escape and unescape, eval

6. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 6 http://www.cs.cityu.edu.hk/~helena Global Functions – isFinite(), isNaN() isFinite() Test whether a value is a finite number (opposite cases: NaN or infinity) Example: isFinite(8%0) and isFinite(9/0)  false If the computation results in NaN or infinity, then false is returned, otherwise true is returned. isNaN() Test whether a value is not-a-number. Example: isNaN(parseInt(document.F1.t1.value)) Application: Check whether a value is a valid number before processing it: /* check a mark and return the grade*/ function convertToGrade(mark) {var x=parseInt(mark); if (isNaN(x)) return 'Wrong'; if (mark>80) return 'A'; else if (mark>65) return 'B'; else if (mark>45) return 'C'; else return 'F'; } Note: To check whether a string value x is empty, simply type if (x=="")

7. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 7 http://www.cs.cityu.edu.hk/~helena Global Functions – escape(), unescape() escape() encode a string by replacing special characters with hexadecimal values like %xx. These are not changed: 0-9, a-z, A-Z, @, *, _, +, -,., / unescape() decode a string that is encoded with escape(). alert ( escape("McDonald's") ) alert ( unescape("McDonald%27s") ) Application: Encoding/decoding processes are needed if we don't want to send special characters across web applications directly [ or not permitted to do so ]. Escape()/unescape() will not appear in test/exam

8. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 8 http://www.cs.cityu.edu.hk/~helena Global Functions – eval() eval() - Evaluates and executes the code in a string. Eg. eval("3+4"), eval("alert('hello')") : The parameter is the string of code to be executed. Interesting : to allow somebody to type codes. But not used frequently in real-world programs. Example: Suppose there is a text box object: document.F1.t1 3+4 then alert (document.F1.t1.value) shows 3+4. alert (eval(document.F1.t1.value)) shows 7. To store the result in a variable x: x=eval(document.F1.t1.value) (1) If it contains: setInterval('alert(Math.random())',1000) then eval(document.F1.t1.value) pops up random numbers every second. (2) If it contains: <input type="button" onclick="eval(document.F1.t1.value)" value="do it"/> eval() will not appear in test/exam

9. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 9 http://www.cs.cityu.edu.hk/~helena Creation of Objects Objects created with the new operator During object creation, a special constructor function is invoked for initialization of the object. The new operator creates a new object and invokes a constructor function to initialize it. new constructor(arguments) Example 1: var now = new Date(); //Current date and time Example 2: var new_years_eve = new Date(2000, 11, 31); // Dec 31, 2000 In the above, Date() is a constructor function that creates a Date object (The Date objects will be covered very soon in this topic. ) As a special case, for the new operator only, omitting the parentheses is allowed: Example 3: var now = new Date; //Current date and time

10. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 10 http://www.cs.cityu.edu.hk/~helena This page may not work in FrontPage. But okay in Internet Explorer. Creation of Objects Even without using the new operator directly, objects can be created as a result of some operations. For example: CS1301 /*show a new window with 10 lines of text*/ function createNewWindow() { var myWindow = window.open(); var i=0; while (i<10) {myWindow.document.write( "This is a new window "); i++; } Create New Window Use the open method to create a new window object. The myWindow variable is defined to receive the new window object. The new window object is referred as myWindow afterwards.

11. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 11 http://www.cs.cityu.edu.hk/~helena The window Object window object - Every web browser window is represented by a window object. Commonly used window methods: alert(), confirm(), prompt()- Simple dialogs resizeTo(), resizeBy()-Change the window size moveTo(), moveBy()-Change the window location open() -Create a blank window or a new window with a specified URL print()- Print the window or frame (same as the File/Print command of the window.) setInterval(), clearInterval()-Schedule or cancel a function to be invoked Commonly used window properties: status- The text that appears in the status bar document- The document object location-The URL of the current document Can be set to load a new document Also provides reload method history-Provides history.back() and history.forward() for traversals Also contains global functions (functions that not really specific to the "window"): eg. parseInt( )

12. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 12 http://www.cs.cityu.edu.hk/~helena The window Object set status bar print set window size to 300x300 decrease width by 30, increase height by 80 Move window to (300,300) Move window by (-30,100) back forward The example below shows the uses of resizeTo (newWidth, newHeight)- Set the window size (in pixels) resizeBy (changeWidth, changeHeight)- Increase or decrease width and height moveTo (newX, newY)- Set the window location (upper left, in pixels) moveBy (changeX, changeY)- Move the window by offset print ()-Print the window or frame (same as the File/Print command of the window.) status - The text that appears in the status bar history -history.back() and history.forward() for traversals

13. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 13 http://www.cs.cityu.edu.hk/~helena The window Object Reload the page window.location The location object represents the URL of the document currently being displayed. Can be set to load a new document, eg. var interest;.. if (interest=='Programming') window.location='http://www.cs.cityu.edu.hk'; else window.location='http://www.cityu.edu.hk';.. Also provides reload method to refresh the page:

14. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 14 http://www.cs.cityu.edu.hk/~helena The window Object function showStatusBarClock() {var now=new Date; window.status=now.toString(); } window.setInterval (code, milliseconds) Schedules a piece of code to run repeatedly. Returns an id that can be passed to window.clearInterval to stop the schedule. window.clearInterval (id) Stops the repeated execution of the code that was started by window.setInterval The following example schedules the status bar clock to be updated every second. Update status bar clock every second Stop the status bar clock

15. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 15 http://www.cs.cityu.edu.hk/~helena The window Object window.open () Create a blank window or a new window with a specified URL. (see a previous slide on Creation of Objects) Examples: //Open a new window to show CS department homepage. window.open("http://www.cs.cityu.edu.hk"); //Open a blank window and then write contents to the document var myWindow = window.open(); myWindow.document.write("This is a new window "); //Open a simple blank window with a given size (in pixels): var myWindow = window.open("","","width=200,height=200"); //Open a simple blank window with a given size and additional features: var myWindow = window.open("","","width=200,height=200,status=yes,resizable=yes");

16. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 16 http://www.cs.cityu.edu.hk/~helena The window Object Arguments of window.open() : window.open(url, name, features) url: Specifies the URL to be displayed. Can be blank for empty document. name: The window name. Can be blank (new window is created). Otherwise if a window with the same name already exists, the open method just returns this existing window. If you need to erase the contents in the window document first, use the open method of the window's document before writing, eg. myWindow.document.open() features: Specifies the size, and window features. size and position: height, width, left, top (in pixels) features: location -address box resizable -can be resized by dragging border scrollbars -display the scrollbars if the size of content exceeds window size status - status bar toolbar menubar

17. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 17 http://www.cs.cityu.edu.hk/~helena The Math Object The Math Object - Can be used for many common mathematical calculations. Provides predefined values like: ConstantDescription Value Math.EBase of a natural logarithm (e). Approximately 2.718 Math.LN2Natural logarithm of 2. Approximately 0.693 Math.LN10Natural logarithm of 10.Approximately 2.302 Math.LOG2EBase 2 logarithm of e.Approximately 1.442 Math.LOG10EBase 10 logarithm of e.Approximately 0.434 Math.PI  Approximately 3.142 Math.SQRT1_2Square root of 0.5.Approximately 0.707 Math.SQRT2Square root of 2.0.Approximately 1.414 Example: to compute the circumstances of a circle with radius 10: var area=Math.PI*10*10 ;

18. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 18 http://www.cs.cityu.edu.hk/~helena The Math Object The Math Object also provides a lot of calculation methods: MethodDescriptionExample Math.abs( x )absolute value of x Math.abs( 7.2 ) is 7.2 Math.abs( 0 ) is 0 Math.abs( -5.6 ) is 5.6 Math.round( x )rounds x to the closest integer Math.round( 9.75 ) is 10 Math.round( 9.25 ) is 9 Math.ceil( x )rounds x to the smallest integer not less than xMath.ceil( 9.2 ) is 10 Math.ceil( -9.8 ) is -9 Math.floor( x )rounds x to the largest integer not greater than xMath.floor( 9.2 ) is 9 Math.floor( -9.8 ) is -10 Math.max(x,y,..)largest value in the list Math.max( 0.1, 2.3, 12.7 ) is 12.7 Math.max( -2.3, -12.7 ) is -2.3 Math.min(x,y,..)smallest value in the list Math.min( 2.3, 12.7 ) is 2.3 Math.min( -2.3, -12.7 ) is -12.7 Question: What are the values returned by:Math.floor(0) Math.floor(9.9999999)

19. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 19 http://www.cs.cityu.edu.hk/~helena The Math Object MethodDescriptionExample Math.exp( x )exponential method exMath.exp( 1.0 ) is 2.71828 Math.exp( 2.0 ) is 7.38906 Math.log( x )natural logarithm of x (base e)Math.log( 2.718282 ) is 1.0 Math.log( 7.389056 ) is 2.0 Math.pow( x, y )x raised to power y (xy)Math.pow( 2, 7 ) is 128 Math.pow( 9, 0.5 ) is 3 Math.sqrt( x )square root of xMath.sqrt( 900 ) is 30 Math.sqrt( 9 ) is 3 Math.cos( x )trigonometric cosine of x (x in radians)Math.cos( 0 ) is 1 Math.cos(Math.PI/3) is 0.5 Math.sin( x )trigonometric sine of x (x in radians)Math.sin( 0 ) is 0 Math.tan( x ) trigonometric tangent of x (x in radians)Math.tan( 0 ) is 0

20. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 20 http://www.cs.cityu.edu.hk/~helena The Math Object Generate Random Numbers The Math.random() method returns a random value between 0 and 0.99999…(less than 1.0). Example: var randomValue = Math.random(); To adjust the range, eg. between 0 and 99.999.., scaling is needed: var randomValue = Math.random()*100; To obtain whole integers, eg. among 0,1,2,99, Math.floor() can be used to cut off the digits after the decimal point: var randomValue = Math.floor(Math.random()*100); Explanation: 0 is obtained if Math.random() gives 0.0000, 0.0001,0.0002,...0.0099 1 is obtained if Math.random() gives 0.0100, 0.0101,0.0102,...0.0199 … 99 is obtained if Math.random() gives 0.9900,0.9901,0.9902,…0.9999 The smallest possible value is : 0 The largest possible value is : 99 0,1,2,..99 are obtained with equal chances (randomness)

21. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 21 http://www.cs.cityu.edu.hk/~helena The Math Object Generate Random Numbers If the range is arbitrary: x, x+1, x+2,..y (totally y-x+1 numbers), Shifting is needed: var randomValue = x + Math.floor(Math.random()*(y-x+1)); For example, if the range is: 40,41,42,..59 (ie. 40,40+1,40+2,..40+19, totally 20 numbers) var randomValue = 40 + Math.floor(Math.random()*20); Explanation: The smallest possible value is : 40 The largest possible value is : 59 (just less than 40+20) 40,41,42,..59 are obtained with equal chances (randomness) Think about it:  How to obtain a random number among 41,43,..60?  How to obtain the random Die Roller numbers (1,2,3,4,5,6)?  How to obtain a random number among 72,43,..88?  How to obtain a random student ID among 50000000 to 50999999?

22. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 22 http://www.cs.cityu.edu.hk/~helena The Date Object (Handle date and time) The Date Object - Provides methods for date and time manipulations. Date and time processing can be based on the computer's (1) local time zone - eg. Our lecture started at 10:30:00 UTC+0800 or(2) World Time Standard's Coordinated Universal Time (UTC) - formerly called Greenwich Mean Time (GMT) - eg. Our lecture started at 02:30:00 UTC Most methods of the Date object have 2 versions for the above. Examples: toString() and toUTCString()

23. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 23 http://www.cs.cityu.edu.hk/~helena The Date Object (Handle date and time) (A)Creation of Date Objects To handle date and time, we need to create a Date object like: var d=new Date(..); new Date() current date and time new Date(milliseconds) milliseconds is number of milliseconds since midnight (UTC) on 1/1/1970. new Date(year, month, day, hours, minutes, seconds, ms) day, hours, minutes, seconds, ms are optional [Note that month values are 0 to 11, meaning Jan to Dec] var d1 = new Date(); var d2 = new Date(1000); var d3 = new Date(2007,2,15,10,30,40); alert(d1.toString()+"\n"+ d2.toString()+"\n"+ d3.toString()+"\n");

24. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 24 http://www.cs.cityu.edu.hk/~helena The Date Object Methods alert(x.toString()) alert(x) //automatically converted to string alert(x.toLocaleString()) alert(x.toUTCString()) (B) Conversion of Date object to a date/time String (1) Obtain DATE and TIME String toString(): use the local time zone. toLocaleString(): use the local time zone and the local date formatting conventions. toUTCString(): use universal time. Example: Given var x =new Date(2006,2,10,15,30);

25. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 25 http://www.cs.cityu.edu.hk/~helena The Date Object Methods (2) Obtain DATE String Only toDateString() (3) Obtain TIME String Only toLocaleTimeString() toLocaleDateString() toTimeString() alert(x.toDateString()) alert(x.toLocaleDateString()) alert(x.toTimeString()) alert(x.toLocaleTimeString())

26. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 26 http://www.cs.cityu.edu.hk/~helena Date MethodsDescription getFullYear(), getUTCFullYear()Returns the year as a four-digit number in local time or UTC. getMonth(), getUTCMonth()Returns a number from 0 (January) to 11 (December) representing the month in local time or UTC. getDate(), getUTCDate()Returns a number from 1 to 31 representing the day of the month in local time or UTC. getDay(), getUTCDay()Returns a number from 0 (Sunday) to 6 (Saturday) representing the day of the week in local time or UTC. getHours(), getUTCHours()Returns a number from 0 to 23 representing hours since midnight in local time or UTC. getMinutes(), getUTCMinutes()Returns a number from 0 to 59 representing the minutes for the time in local time or UTC. getSeconds(), getUTCSeconds()Returns a number from 0 to 59 representing the seconds for the time in local time or UTC. getMilliseconds(), getUTCMilliSeconds()Returns a number from 0 to 999 representing the number of milliseconds in local time or UTC. getTime()Returns the number of milliseconds between January 1, 1970 and the time in the Date object. getTimezoneOffset()Returns the difference in minutes between the current time on the local computer and UTC. (C) Conversion of Date/Time data to numbers

27. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 27 http://www.cs.cityu.edu.hk/~helena Date MethodsDescription setFullYear(y,m,d), setUTCFullYear(y,m,d)Sets the year in local time or UTC. m and d are optional. setMonth(m,d), setUTCMonth(m,d)Sets the month in local time or UTC. d is optional. setDate(d), setUTCDate(d)Sets the day of the month (1 to 31) in local time or UTC. setHours(h,m,s,ms), setUTCHours(h,m,s,ms)Sets the hour in local time or UTC. m, s, and ms are optional. setMinutes(m,s,ms), setUTCMinutes(m,s,ms)Sets the minute in local time or UTC. s and ms are optional. setSeconds(s,ms), setUTCSeconds(s,ms)Sets the second in local time or UTC. ms is optional. setMilliSeconds(ms), setUTCMilliseconds(ms)Sets the number of milliseconds in local time or UTC. setTime(ms)Sets the time based on its argument—the number of elapsed milliseconds since January 1, 1970. * Meaning of arguments listed above: y: year, m: month or minute, d: date, h: hour, s: second, ms: millisecond. * For each optional argument: if not specified, the current value in the Date object is used. (D) Override Date/Time data with numbers

28. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 28 http://www.cs.cityu.edu.hk/~helena The Date Object : Application Application: The Date Navigator The page contains dd, mm, yyyy fields for a date. Users can type in these fields. Two buttons are available for moving the date forward and backward by one day. On loading, the date fields are initialized to the current date. Date Navigator / (dd/mm/yyyy)

29. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 29 http://www.cs.cityu.edu.hk/~helena //Initialize the date fields to current day. function setup() {var today=new Date; //current date and time document.F1.d.value=today.getDate(); document.F1.m.value=today.getMonth()+1; document.F1.y.value=today.getYear(); } //Advance the shown date to the next day. function showNextDay() {var shownDate, newDate, nMilliSeconds; //1. Create a date object for the form data ==> shownDate shownDate=new Date(document.F1.y.value,document.F1.m.value-1,document.F1.d.value); //2. Create a date object for the new date ==> newDate nMilliSeconds=shownDate.getTime(); //elapsed milliseconds since January 1, 1970. newDate=new Date(nMilliSeconds+1000*60*60*24); //add milliseconds of 24 hours. //3. Update the form with newDate document.F1.d.value=newDate.getDate(); document.F1.m.value=newDate.getMonth()+1; document.F1.y.value=newDate.getYear(); } The setup() and showNextDay() functions //Initialize the date fields to current day. function setup() {var today=new Date; //current date and time document.F1.d.value=today.getDate(); document.F1.m.value=today.getMonth()+1; document.F1.y.value=today.getFullYear(); } //Advance the shown date to the next day. function showNextDay() {var shownDate, newDate, nMilliSeconds; //1. Create a date object for the form data ==> shownDate shownDate=new Date(document.F1.y.value,document.F1.m.value-1,document.F1.d.value); //2. Create a date object for the new date ==> newDate nMilliSeconds=shownDate.getTime(); //elapsed milliseconds since 1/1/1970. newDate=new Date(nMilliSeconds+1000*60*60*24); //add ms of 24 hours. //3. Update the form with newDate document.F1.d.value=newDate.getDate(); document.F1.m.value=newDate.getMonth()+1; document.F1.y.value=newDate.getFullYear(); } Demonstration of : 3 kinds of Date constructors, getDate(), getMonth(), getYear() getTime()

30. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 30 http://www.cs.cityu.edu.hk/~helena 1.Create a date object x (current date and time). 2.Update day, month, year of x based on the form data. 3.Find new value for x. 4.Display x in the form. //Advance the shown date to the next day. function showNextDay() {var nMilliSeconds; var x=new Date; x.setYear(document.F1.y.value); x.setMonth(document.F1.m.value-1); x.setDate(document.F1.d.value); nMilliSeconds=x.getTime(); //elapsed milliseconds since 1/1/1970. x.setTime(nMilliSeconds+1000*60*60*24); //add ms of 24 hours. document.F1.y.value=x.getFullYear(); document.F1.m.value=x.getMonth()+1; document.F1.d.value=x.getDate(); } Your exercises: Finish the showPrevDay function. Add two buttons for moving 10 days backward and forward. Demonstration of : setDate(), setMonth(), setYear() instead of using the Date(yyyy,mm,dd..) constructor setTime() - instead of using the Date(milliseconds) constructor Another version of showNextDay()

31. (CS1301) Introduction to Computer Programming City Univ of HK / Dept of CS / Helena Wong 6. Functions and Objects I - 31 http://www.cs.cityu.edu.hk/~helena Summary Introduction to JavaScript Objects and HTML Element Objects Global Functions: isFinite, isNaN, escape/unescape, eval Creation of Objects: the new operator and constructor functions Commonly used objects: Window: status, location, resizeTo, …, setInterval, clearInterval, open (new window) Math: constants (E, LN2, PI,...) and methods(floor, max, sqrt...)  Random Number Generation Date: Constructors, conversion to string, getXX and setXXX methods  Application: Date Navigator