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1 Tutorial 2: Working with Operators and Expressions TRUE/FALSE 1. You can add a dynamic effect to a Web site using ontime processing. ANS: F PTS: 1 REF: JVS You can not insert values into a Web form s fields. ANS: F PTS: 1 REF: JVS An event is an action that occurs within a Web browser or Web document. ANS: T PTS: 1 REF: JVS In the code <body onload = "myfunction()"...>, myfunction() is executed when the page loads. ANS: T PTS: 1 REF: JVS Across the different web browsers and their versions, there is support for the same set of events. ANS: F PTS: 1 REF: JVS The time object is used in JavaScript to work with dates. ANS: F PTS: 1 REF: JVS You use the thisdate() function to get the current date and time. ANS: F PTS: 1 REF: JVS The getdate() method returns the specific month for a particular date. ANS: F PTS: 1 REF: JVS To get a two digit year, you use the getyear() method. ANS: T PTS: 1 REF: JVS JavaScript only allows the minutes and seconds to be retrieved from a date. ANS: F PTS: 1 REF: JVS JavaScript does not support daylight savings time. ANS: T PTS: 1 REF: JVS When writing your own function, you begin by using the word "method". ANS: F PTS: 1 REF: JVS 63

2 13. Binary operators work on only one operand. ANS: F PTS: 1 REF: JVS You use the ++ operator to increment a variable in JavaScript. ANS: T PTS: 1 REF: JVS To avoid misunderstanding the actions of a decrement operator, read the action of the operator from right to left. ANS: F PTS: 1 REF: JVS If you insert a space between the two symbols of the assignment operator, JavaScript will report a syntax error. ANS: T PTS: 1 REF: JVS JavaScript measures time in terms of days. ANS: F PTS: 1 REF: JVS To use the round method, you type "math.round()". ANS: F PTS: 1 REF: JVS The Math.random() method returns a value between 0 and 1. ANS: T PTS: 1 REF: JVS The value.tofixed(n) method can be used to control the number of digits displayed by the browser. ANS: T PTS: 1 REF: JVS 80 MODIFIED TRUE/FALSE 1. One way of inserting an event handler is to add it as an attribute of the element in the Web document. ANS: T PTS: 1 REF: JVS The onclick event handler handles when the mouse button has been pressed. ANS: F, onmousedown PTS: 1 REF: JVS Another way to run a JavaScript command in response to an event is to treat it as a hypertext form. ANS: F, link

PTS: 1 REF: JVS 58 4. To create a date object, you use new Time(). ANS: F, new Date() PTS: 1 REF: JVS 59 5. The time methods can be used to retrieve information from a date object.

3 PTS: 1 REF: JVS To create a date object, you use new Time(). ANS: F, new Date() PTS: 1 REF: JVS The time methods can be used to retrieve information from a date object. ANS: F, date PTS: 1 REF: JVS The method to get the current hour from a date object is DateObject.getTimeHour(). ANS: F DateObject.getHours() PTS: 1 REF: JVS The gettime() method retrieves the time value as expressed in milliseconds. ANS: T PTS: 1 REF: JVS The operators shown in the figure above are binary operators. ANS: F, unary PTS: 1 REF: JVS The -- operator in the figure above is used to decrement variables. ANS: T PTS: 1 REF: JVS To make a function available to other pages, you should place the function in an external file.

ANS: T PTS: 1 REF: JVS 64 11. The figure above shows an example of a JavaScript object. ANS: F, function PTS: 1 REF: JVS 69 12.

4 ANS: T PTS: 1 REF: JVS The figure above shows an example of a JavaScript object. ANS: F, function PTS: 1 REF: JVS The portion of JavaScript code pointed at in the figure above calculates the number of seconds in a day. ANS: F, milliseconds PTS: 1 REF: JVS The && is a(n) comparison operator. ANS: F, logical PTS: 1 REF: JVS To cancel a time-delayed command called timeone, you would use timeone.cleartimeout(). ANS: F, cleartimeout(timeone) PTS: 1 REF: JVS In the following JavaScript code: settimeout("addthree()",50); settimeout("showdate()",50); the functions execute almost simultaneously.

5 ANS: T PTS: 1 REF: JVS 89 MULTIPLE CHOICE 1. In document.contact.name.value, the name of the form must be. a. Contact c. document b. Name d. value ANS: A PTS: 1 REF: JVS A(n) is a statement that tells browsers what code to run in response to the specified event. a. event script c. unary operator b. event handler d. element attribute ANS: B PTS: 1 REF: JVS The event handler runs when the browser has completed unloading the document. a. onload c. onerror b. onremove d. onunload ANS: D PTS: 1 REF: JVS The event handler tests whether or not a user has pressed and released a button on the keyboard. a. onquit c. onkeydown b. onclick d. onkeypress ANS: D PTS: 1 REF: JVS If a user clicks an item on a page, which event(s) may occur? a. ondblclick c. a only b. onclick d. either a or b ANS: D PTS: 1 REF: JVS The event handler runs when a user has entered a text input field. a. onload c. onfocus b. onchange d. onblur ANS: C PTS: 1 REF: JVS To add code that runs when content of an input field has been modified, you use the event handler. a. onload c. onfocus b. onchange d. onblur ANS: B PTS: 1 REF: JVS To have the function verify() execute when a person leaves the Name input field, you must use the event handler. a. onload c. onfocus b. onchange d. onblur ANS: D PTS: 1 REF: JVS To give buttons an action on a form, you can use the event. a. onblur c. onkeypress

6 b. onclick d. onchange ANS: B PTS: 1 REF: JVS Which of the following is not a Window event? a. onresize c. onscroll b. onselect d. onmove ANS: B PTS: 1 REF: JVS Which of the following is not a mouse event? a. onmousedown c. onmouseclick b. onmouseup d. onmouseout ANS: C PTS: 1 REF: JVS Which of the following is not a keyboard event? a. onkeyout c. onkeypress b. onkeydown d. none of the above ANS: A PTS: 1 REF: JVS Older web browsers used links to run JavaScript commands. a. paragraph c. hypertext b. image d. source ANS: C PTS: 1 REF: JVS A function includes its, which are values used by the function. a. terms c. ids b. parameters d. names ANS: B PTS: 1 REF: JVS is the general syntax for using anchor tags to run JavaScript. a. <a alt = "javascript:script">content</a> c. <a href = "javascript:script">content</a> b. <a href = "script">content</a> d. <a src = "javascript:script">content</a> ANS: C PTS: 1 REF: JVS To create a date object using the current date and store it in mydate, you enter. a. mydate = new Date(); b. mydate = new Time(); c. mydate = new Time(2011, 1, 24, 14, 35, 5); d. mydate = new Date(2011, 1, 24, 14, 35, 5); ANS: A PTS: 1 REF: JVS January is indicated by the number in JavaScript. a. 0 c. 4 b. 1 d. 10 ANS: A PTS: 1 REF: JVS Dates are numeric values measured in. a. milliseconds c. microseconds b. nanoseconds d. picoseconds

7 ANS: A PTS: 1 REF: JVS The method always returns the year in four digit format. a. getyear(); c. getdate(); b. getfulldate(); d. getfullyear(); ANS: D PTS: 1 REF: JVS The starting date for time calculations is. a. January 1, 1970 c. January 1, 1900 b. January 1, 1990 d. January 1, 1960 ANS: A PTS: 1 REF: JVS After the following code, what value does x contain? x = new Date("October 31, :22:05"); x = x.getminutes(); a. 31 c. 11 b. 22 d. 5 ANS: B PTS: 1 REF: JVS When the somedate variable stores the date object for "June 15, :35:28" (which is a Wednesday), the method would return a value of 3. a. somedate.getdate(); c. somedate.gettime(); b. somedate.getmonth(); d. somedate.getday(); ANS: D PTS: 1 REF: JVS To change the somedate variable s year to 2012, you enter. a. somedate.setyear(12); c. somedate.setfullyear(2012); b. somedate.setfullyear(12); d. somedate.setyear(2012); ANS: C PTS: 1 REF: JVS Which of the following includes support for daylight savings time? a. computer s operating system c. Date methods b. JavaScript d. all of the above ANS: A PTS: 1 REF: JVS Consider the following code: function showbirthday(birthday) { thisday = birthday.getdate(); thismonth = birthday.getmonth()+1; thisyear = birthday.getfullyear(); return thismonth + "/" + thisday + "/" + thisyear; } What type of parameter must birthday be? a. time object c. check object b. date object d. none of the above ANS: B PTS: 1 REF: JVS 63

8 26. The method extracts the year value from the date variable. a. extractyear() c. Year() b. getfullyear() d. thisyear() ANS: B PTS: 1 REF: JVS To make JavaScript code available to other web pages, the code should be placed in. a. the head of the document c. an external file b. an internal script tag d. a CSS file ANS: C PTS: 1 REF: JVS To tell the browser to include code from the mycode.js file, you should enter. a. <script type="text/javascript" link="mycode.js"> b. <script type="text/javascript" file="mycode.js"> c. <script type="text/javascript" href="mycode.js"> d. <script type="text/javascript" src="mycode.js"> ANS: D PTS: 1 REF: JVS In a <script> tag linking an external JavaScript file, the MIME type should be specified as. a. file/javascript c. mime/javascript b. text/javascript d. src/javascript ANS: B PTS: 1 REF: JVS To perform a calculation, a statement must include a(n). a. operator c. script file b. link d. none of the above ANS: A PTS: 1 REF: JVS A(n) operator can be used to perform simple mathematical calculations. a. conditional c. ordinal b. logical d. arithmetic ANS: D PTS: 1 REF: JVS The operator increases a value by 1 (unary operator). a. + c. ++ b. * d. ~ ANS: C PTS: 1 REF: JVS operators work on two elements in an expression. a. Binary c. Unary b. Tertiary d. Increment ANS: A PTS: 1 REF: JVS operators work on only one variable. a. Binary c. Solo b. Unary d. Increment ANS: B PTS: 1 REF: JVS 67

9 35. The most common assignment operator is the. a. += c. = b. -= d. == ANS: C PTS: 1 REF: JVS The expression to return the remainder of x divided by y would be. a. x / y c. y / x b. y % x d. x % y ANS: D PTS: 1 REF: JVS In JavaScript, the expression creates the same result as the expression x = x + y;. a. y += x c. y = x ++ y b. x = x++ d. x += y ANS: D PTS: 1 REF: JVS What does the following generic function called foo return? function foo() { var y = 3; var x = 4; y = --x; x = y++ % x; return y; } a. 4 c. 0 b. 3 d. 5 ANS: A PTS: 1 REF: JVS Which of the following calculates the difference in terms of days? a. days = (newyear - currentdate)/(1000*60*60); b. days = (newyear - currentdate)/(1000*60*24); c. days = (newyear - currentdate); d. days = (newyear - currentdate)/(1000*60*60*24); ANS: D PTS: 1 REF: JVS The can be used for performing advanced calculations and mathematical operations. a. Date object c. Library object b. Math object d. All of the above ANS: B PTS: 1 REF: JVS To change x's value to the nearest integer, you would use the following code: a. Math.round(x); c. math.round(x); b. Math.exp(x); d. math.ceil(x); ANS: A PTS: 1 REF: JVS When using a random number, the function you would least likely use to get an integer value would be.

10 a. Math.round() c. Math.ceil() b. Math.floor() d. none of the above ANS: A PTS: 1 REF: JVS The constant has the approximate value of a. Math.X c. Math.PI b. Math.E d. All of the above ANS: C PTS: 1 REF: JVS To display x with only 2 digits, you can apply the method. a. numdigits c. fixdigits b. tofixed d. tocurrency ANS: B PTS: 1 REF: JVS If x has the value , x.tofixed(3) returns what value? a c. $5.13 b. $5.135 d ANS: D PTS: 1 REF: JVS The method returns a text string with n significant digits to the left or right of the decimal point. a. toprecision c. toexponential b. tofixed d. todigits ANS: A PTS: 1 REF: JVS Given the following code: var result = 10/"A"; document.write(result); What value will be displayed? a. N/A c. NaN b. NonN d. infinity ANS: C PTS: 1 REF: JVS Which function makes sure that a number is not greater than the largest numeric value supported by JavaScript? a. isnan(value) c. iszero(value) b. isnull(value) d. isfinite(value) ANS: D PTS: 1 REF: JVS When displaying the value , JavaScript shows digits by default. a. 0 c. 4 b. 2 d. 6 ANS: D PTS: 1 REF: JVS If x has the value of 5, then to convert it to a text string, you could use. a. mystring = x; c. mystring = parsetext(x); b. mystring = x + ""; d. none of the above ANS: B PTS: 1 REF: JVS 80

11 51. converts a text string, mystring, to a number with decimal places. a. parsetext c. parsedecimal b. parseint d. parsefloat ANS: D PTS: 1 REF: JVS Which of the following returns NaN? a. parseint("the number of barrels was 12"); b. parseint("135.6"); c. parseint("3 books were read"); d. none of the above ANS: A PTS: 1 REF: JVS The general format of the conditional operator is. a. (condition) : falsevalue? truevalue c. (condition)? falsevalue : truevalue b. (condition) : truevalue : falsevalue d. (condition)? truevalue : falsevalue ANS: D PTS: 1 REF: JVS The comparison operator returns true if variables are equal. a.!= c. >= b. == d. <= ANS: B PTS: 1 REF: JVS The comparison operator returns true if variables are not equal. a. ~= c.!= b. == d. ++ ANS: C PTS: 1 REF: JVS The logical operator returns true when both expressions are true. a. c. == b. d. && ANS: D PTS: 1 REF: JVS The logical operator returns true when either expression is true. a. c. == b. d. && ANS: A PTS: 1 REF: JVS The logical operator returns true if the expression is false and false if the expression is true. a. c. && b.! d. == ANS: B PTS: 1 REF: JVS Which of the following assigns y a value of 20 if x is greater than 1 and less than 3 and 15 otherwise? a. y = (x > 1) && (x < 3) : 20? 15; c. y = (x > 1) && (x < 3)? 20 : 15; b. y = (x > 1) && (x < 3)? 15 : 20; d. y = (x > 1) (x < 3)? 20 : 15; ANS: C PTS: 1 REF: JVS 84

60. Using the figure above, if thishour is 21, what values will be stored in ampm and thishour after the last line of code? a. p.m., 9 c. p.m. 10 b. a.m., 9 d. a.m., 8 ANS: A PTS: 1 REF: JVS 85 61.

12 60. Using the figure above, if thishour is 21, what values will be stored in ampm and thishour after the last line of code? a. p.m., 9 c. p.m. 10 b. a.m., 9 d. a.m., 8 ANS: A PTS: 1 REF: JVS A(n) command runs after a specific amount of time. a. time-delayed c. delayed b. interval-run d. time-interval ANS: A PTS: 1 REF: JVS The general format of the command to specify that a task occur once, after some time, is. a. settime("command", interval); c. settimeout("command", delay); b. setdelay("command", interval) d. setinterval("command", delay); ANS: C PTS: 1 REF: JVS To indicate that the displaylist() method should run once, 15 milliseconds after the page loads, you would use. a. onload = "settimeout("displaylist()", 15);" b. onload = "settimeout('displaylist()', 15);" c. onload = "setinterval("displaylist()", 15);" d. onload = "setinterval('displaylist()', 15);" ANS: A PTS: 1 REF: JVS To give an identification to a command set to run once after a delay, the general syntax is. a. timeid = setinterval("command",delay); b. timeid = setdelay("command",delay); c. timeid = setidtimeout("command",delay); d. timeid = settimeout("command",delay); ANS: D PTS: 1 REF: JVS Which of the following clears only the command called mydelay that has been set to run once after 30 seconds? a. clearinterval(mydelay); c. cleartimeout(mydelay); b. clearinterval(); d. cleartimeout(); ANS: C PTS: 1 REF: JVS A(n) command instructs a browser to run the same command repeatedly. a. timed-interval c. time-delayed

13 b. interval-run d. delayed ANS: A PTS: 1 REF: JVS Which of the following clears only the command called mydelay that has been set to run every 25 seconds? a. cleartimeout(mydelay); c. clearinterval(mydelay); b. clearinterval(); d. cleartimeout(); ANS: C PTS: 1 REF: JVS To give an identification to a command set to run repeatedly after a certain amount of time, the general syntax is. a. timeid = settimeout("command",interval); b. timeid = setdelay("command",interval); c. timeid = setidtimeout("command",interval); d. timeid = setinterval("command",interval); ANS: D PTS: 1 REF: JVS Given the following code, which function starts running at 30 milliseconds? settimeout("superclock()",30); settimeout("updatemenu()",30); settimeout("performcalc()",30); a. superclock() c. performcalc() b. updatemenu() d. all of the above ANS: D PTS: 1 REF: JVS To clear all commands set to repeat, you use. a. cleartimeout() c. cleardelay() b. clearrepeat() d. clearinterval() ANS: D PTS: 1 REF: JVS 88 Case-Based Critical Thinking Questions Case 2-1 Legend Films is planning to create a page that will allow users to their video requests for the studio to add to their online video offerings. 71. In order to add the date to the form, the Web designer could use the object. a. Math c. Arithmetic b. Comparison d. Date ANS: D PTS: 1 REF: JVS 59 TOP: Critical Thinking 72. The Web designer would like to create code that could be used in each movie new release page to count down to the release. Where should he place the code to make it easy to reuse? a. in a script tag c. in an external file b. in the head of the document d. none of the above ANS: C PTS: 1 REF: JVS 64 TOP: Critical Thinking 73. External files containing JavaScript commonly use the extension.

14 a. asp c. js b. script d. php ANS: C PTS: 1 REF: JVS 65 TOP: Critical Thinking Case-Based Critical Thinking Questions Case 2-2 Carol Smith wants to create a page that would have several dynamic effects. For instance, she wants a clock that shows how long the user has been viewing a page as well as to have the page show a welcome message and a goodbye message. She also has a list of links that should run her functions to update parts of the page. 74. Carol wants to have the clock update every 10 seconds. Which method would be best for her to use to cause her script to run according to her schedule? a. setinterval c. settimeout b. setdelay d. none of the above ANS: A PTS: 1 REF: JVS 88 TOP: Critical Thinking 75. Carol will most likely use which event to display her welcome message? a. onenter c. onunload b. onexit d. onload ANS: D PTS: 1 REF: JVS 57 TOP: Critical Thinking 76. The goodbye message will most likely involve using the event. a. onenter c. onunload b. onexit d. onload ANS: C PTS: 1 REF: JVS 57 TOP: Critical Thinking 77. Since Carol is using a list of links to activate JavaScript commands, she will need to use a(n) even though it is no longer considered good design. a. hypertext link c. onclick event b. external file d. onload event ANS: A PTS: 1 REF: JVS 58 TOP: Critical Thinking Case-Based Critical Thinking Questions Case 2-3 Betty's Custom Floral Arrangements shop has an online order form. She has added some JavaScript functions to calculate how much a person has to pay before they submit the page, and now wants to add her functions to her form buttons. 78. Which event is best used for her buttons? a. ondblclick c. onclick b. onkeypress d. onmouseout ANS: C PTS: 1 REF: JVS 57 TOP: Critical Thinking 79. Betty wants to display the total from her calctotal() function in her form named results in a text box called finalamount. What will the command look like? a. results.finalamount.document.value = calctotal(); b. document.finalamount.results = calctotal();

15 c. document.finalamount.results.value = calctotal(); d. document.results.finalamount.value = calctotal(); ANS: D PTS: 1 REF: JVS 55 TOP: Critical Thinking 80. Betty gets complaints that customers are seeing NaN in certain places. What function can help her stop that from happening? a. isfin c. isnan b. isnumber d. isfinite ANS: C PTS: 1 REF: JVS 79 TOP: Critical Thinking COMPLETION 1. A(n) is an attribute added to a Web page element that specifies a program to be run in response to an event. ANS: event handler PTS: 1 REF: JVS The event handler executes when the mouse button is released. ANS: onmouseup PTS: 1 REF: JVS A(n) object is an object containing date information. ANS: date PTS: 1 REF: JVS The keyword indicates that you are creating a new object. ANS: new PTS: 1 REF: JVS To extract the day of the month from a given date object, JavaScript provides the method. ANS: getdate() getdate PTS: 1 REF: JVS The method exists for extracting the value of the current month from a date object. ANS: getmonth() getmonth

16 PTS: 1 REF: JVS The method can be used to set the time of a Date object in milliseconds since January 1, ANS: settime() settime PTS: 1 REF: JVS A(n) is a symbol used to act upon an item or a variable within a JavaScript expression. ANS: operator PTS: 1 REF: JVS The + operator belongs to a group of operators called operators, which perform simple mathematical calculations. ANS: arithmetic PTS: 1 REF: JVS The operator can be used to increase the value of a variable by 1. ANS: increment ++ PTS: 1 REF: JVS To subtract one from a variable named count before using it, you should use the operator. ANS: decrement -- PTS: 1 REF: JVS In "y = ++x;", x is before y is assigned a value. ANS: incremented PTS: 1 REF: JVS When subtracting one date from another, the answer is measured in. ANS: milliseconds PTS: 1 REF: JVS 70

17 14. A(n) statement is one that runs only when specific conditions are met. ANS: conditional PTS: 1 REF: JVS A(n) operator compares the value of one element with that of another. ANS: comparison PTS: 1 REF: JVS " x = y== 2? 45 : 50;" is an example of a(n). ANS: conditional conditional operator PTS: 1 REF: JVS The operator returns true if two expressions are true. ANS: && PTS: 1 REF: JVS If x has the value of false, then!x returns. ANS: true PTS: 1 REF: JVS A(n) command runs once after a specified amount of time passes. ANS: time-delayed PTS: 1 REF: JVS If you have six commands set with an interval of 100, they will all run at the time. ANS: same PTS: 1 REF: JVS 89 MATCHING Identify the letter of the choice that best matches the phrase or definition. a. arithmetic operator g. binary operator b. negation operator h. logical operator c. conditional operator i. comparison operator d. date object j. Math object

18 e. unary operator k. increment operator f. date method l. event handler 1. Allows you to connect several expressions 2. A ternary operator that executes a test 3. Has methods for rounding numbers 4. Requires two operands 5. Used to create expressions that have true or false values 6. Perform simple calculations 7. Changes an item's sign 8. Can be placed before or after an operand 9. Requires one operand 10. Tells browsers what code to run 11. Retrieves information from a date object 12. Created using Date(); 1. ANS: H PTS: 1 REF: JVS ANS: C PTS: 1 REF: JVS ANS: J PTS: 1 REF: JVS ANS: G PTS: 1 REF: JVS ANS: I PTS: 1 REF: JVS ANS: A PTS: 1 REF: JVS ANS: B PTS: 1 REF: JVS ANS: K PTS: 1 REF: JVS ANS: E PTS: 1 REF: JVS ANS: L PTS: 1 REF: JVS ANS: F PTS: 1 REF: JVS ANS: D PTS: 1 REF: JVS 59 ESSAY 1. Given a date object Date( June 15, 2011, 14:35:28 ) stored in a variable called Today, list six date methods to extract and display individual component values of this date object. (Note: this date is a Wednesday.) ANS: Today.getSeconds() [value is 28] Today.getMinutes() [value is 35] Today.getHours() [value is 14] Today.getDate() [value is 15] Today.getDay() [value is 3] Today.getMonth() [value is 5] Today.getFullYear() [value is 2011] Today.getTime() [value is 1,308,166,505,000]. PTS: 1 REF: JVS 59 JVS 62 TOP: Critical Thinking 2. List the assignment operators and describe each one.

19 ANS: = Assigns the value of the expression on the right to the expression on the left += Adds two expressions = Subtracts the expression on the right from the expression on the left *= Multiplies two expressions %= Calculates the remainder from dividing the expression on the left by the expression on the right. PTS: 1 REF: JVS 69 TOP: Critical Thinking 3. Write the methods to run a command after a delay, to repeat a command at set intervals, to cancel a time-delayed command, and to cancel a repeated command. ANS: To run a command after a delay, use the method: timeid = settimeout( command,delay); where command is the command to be run, delay is the delay time in milliseconds, and timeid is a variable that stores the id associated with the time-delayed command. To repeat a command at set intervals, use the method: timeid = setinterval( command, interval); where interval is the interval, in milliseconds, before the command is to run again. To cancel a time-delayed command, use the method: cleartimeout(timeid); where timeid is the id of the time-delayed command. To clear all time-delayed commands, use the method cleartimeout(). To cancel a repeated command, use the method: clearinterval(timeid); where timeid is the id of the repeated command. To clear all repeated commands, use the method clearinterval(). PTS: 1 REF: JVS 87 JVS 89 TOP: Critical Thinking

LECTURE-3. Exceptions JS Events. CS3101: Programming Languages: Javascript Ramana Isukapalli

LECTURE-3. Exceptions JS Events. CS3101: Programming Languages: Javascript Ramana Isukapalli LECTURE-3 Exceptions JS Events 1 EXCEPTIONS Syntax and usage Similar to Java/C++ exception handling try { // your code here catch (excptn) { // handle error // optional throw 2 EXCEPTIONS EXAMPLE