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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 54

2. You can not insert values into a Web form’s fields.


3. An event is an action that occurs within a Web browser or Web document.

ANS: T PTS: 1 REF: JVS 56

4. In the code <body onload = "myFunction()" ...>, myFunction() is executed when the page loads.


5. Across the different web browsers and their versions, there is support for the same set of events.


6. The time object is used in JavaScript to work with dates.


7. You use the thisDate() function to get the current date and time.


8. The getDate() method returns the specific month for a particular date.


9. To get a two digit year, you use the getYear() method.


10. JavaScript only allows the minutes and seconds to be retrieved from a date.


11. JavaScript does not support daylight savings time.


12. When writing your own function, you begin by using the word "method".


13. Binary operators work on only one operand.


14. You use the ++ operator to increment a variable in JavaScript.


15. To avoid misunderstanding the actions of a decrement operator, read the action of the operator from right to left.


16. If you insert a space between the two symbols of the assignment operator, JavaScript will report a syntax error.


17. JavaScript measures time in terms of days.


18. To use the round method, you type "math.round()".


19. The Math.random() method returns a value between 0 and 1.


20. The value.toFixed(n) method can be used to control the number of digits displayed by the browser.


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. _________________________


2. The onclick event handler handles when the mouse button has been pressed. _________________________

ANS: F, onmousedown

PTS: 1 REF: JVS 57

3. 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. _________________________

ANS: F, date

PTS: 1 REF: JVS 60

6. The method to get the current hour from a date object is DateObject.getTimeHour(). _________________________

ANS: FDateObject.getHours()

PTS: 1 REF: JVS 61

7. The getTime() method retrieves the time value as expressed in milliseconds. _________________________


8. The operators shown in the figure above are binary operators. _________________________

ANS: F, unary

PTS: 1 REF: JVS 68

9. The -- operator in the figure above is used to decrement variables. _________________________


10. To make a function available to other pages, you should place the function in an external file. _________________________


11. The figure above shows an example of a JavaScript object. _________________________

ANS: F, function

PTS: 1 REF: JVS 69

12. 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 70

13. The && is a(n) comparison operator. _________________________

ANS: F, logical

PTS: 1 REF: JVS 84

14. To cancel a time-delayed command called timeOne, you would use timeOne.clearTimeout(). _________________________

ANS: F, clearTimeout(timeOne)

PTS: 1 REF: JVS 88

15. In the following JavaScript code:

setTimeout("addThree()",50); setTimeout("showDate()",50);

the functions execute almost simultaneously. _________________________


MULTIPLE CHOICE

1. In document.Contact.Name.value, the name of the form must be ____.a. Contact c. documentb. Name d. value

ANS: A PTS: 1 REF: JVS 55

2. A(n) ____ is a statement that tells browsers what code to run in response to the specified event.a. event script c. unary operatorb. event handler d. element attribute

ANS: B PTS: 1 REF: JVS 56

3. The ____ event handler runs when the browser has completed unloading the document.a. onload c. onerrorb. onremove d. onunload

ANS: D PTS: 1 REF: JVS 57

4. The ____ event handler tests whether or not a user has pressed and released a button on the keyboard.a. onquit c. onkeydownb. onclick d. onkeypress


5. If a user clicks an item on a page, which event(s) may occur?a. ondblclick c. a onlyb. onclick d. either a or b


6. The ____ event handler runs when a user has entered a text input field.a. onload c. onfocusb. onchange d. onblur

ANS: C PTS: 1 REF: JVS 57

7. To add code that runs when content of an input field has been modified, you use the ____ event handler.a. onload c. onfocusb. onchange d. onblur


8. To have the function verify() execute when a person leaves the Name input field, you must use the ____ event handler.a. onload c. onfocusb. onchange d. onblur


9. To give buttons an action on a form, you can use the ____ event.a. onblur c. onkeypress

b. onclick d. onchange


10. Which of the following is not a Window event?a. onresize c. onscrollb. onselect d. onmove


11. Which of the following is not a mouse event?a. onmousedown c. onmouseclickb. onmouseup d. onmouseout


12. Which of the following is not a keyboard event?a. onkeyout c. onkeypressb. onkeydown d. none of the above


13. Older web browsers used ____ links to run JavaScript commands.a. paragraph c. hypertextb. image d. source


14. A function includes its ____, which are values used by the function.a. terms c. idsb. parameters d. names


15. ____ 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>


16. 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);


17. January is indicated by the number ____ in JavaScript.a. 0 c. 4b. 1 d. 10


18. Dates are numeric values measured in ____.a. milliseconds c. microsecondsb. nanoseconds d. picoseconds


19. The ____ method always returns the year in four digit format.a. getYear(); c. getDate();b. getFullDate(); d. getFullYear();


20. The starting date for time calculations is ____.a. January 1, 1970 c. January 1, 1900b. January 1, 1990 d. January 1, 1960


21. After the following code, what value does x contain?

x = new Date("October 31, 2011 11:22:05");x = x.getMinutes();a. 31 c. 11b. 22 d. 5


22. When the someDate variable stores the date object for "June 15, 2011 14:35:28" (which is a Wednesday), the ____ method would return a value of 3.a. someDate.getDate(); c. someDate.getTime();b. someDate.getMonth(); d. someDate.getDay();


23. 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);


24. Which of the following includes support for daylight savings time?a. computer’s operating system c. Date methodsb. JavaScript d. all of the above


25. 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 objectb. date object d. none of the above


26. The ____ method extracts the year value from the date variable.a. extractYear() c. Year()b. getFullYear() d. thisYear()


27. To make JavaScript code available to other web pages, the code should be placed in ____.a. the head of the document c. an external fileb. an internal script tag d. a CSS file


28. 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">


29. In a <script> tag linking an external JavaScript file, the MIME type should be specified as ____.a. file/javascript c. mime/javascriptb. text/javascript d. src/javascript


30. To perform a calculation, a statement must include a(n) ____.a. operator c. script fileb. link d. none of the above


31. A(n) ____ operator can be used to perform simple mathematical calculations.a. conditional c. ordinalb. logical d. arithmetic


32. The ____ operator increases a value by 1 (unary operator).a. + c. ++b. * d. ~


33. ____ operators work on two elements in an expression.a. Binary c. Unaryb. Tertiary d. Increment


34. ____ operators work on only one variable.a. Binary c. Solob. Unary d. Increment


35. The most common assignment operator is the ____.a. += c. =b. -= d. ==


36. The expression to return the remainder of x divided by y would be ____.a. x / y c. y / xb. y % x d. x % y


37. In JavaScript, the expression ____ creates the same result as the expression x = x + y;.a. y += x c. y = x ++ yb. x = x++ d. x += y


38. 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. 0b. 3 d. 5


39. 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);


40. The ____ can be used for performing advanced calculations and mathematical operations.a. Date object c. Library objectb. Math object d. All of the above


41. 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);


42. When using a random number, the function you would least likely use to get an integer value would be ____.

a. Math.round() c. Math.ceil()b. Math.floor() d. none of the above


43. The ____ constant has the approximate value of 3.1416.a. Math.X c. Math.PIb. Math.E d. All of the above


44. To display x with only 2 digits, you can apply the ____ method.a. numDigits c. fixDigitsb. toFixed d. toCurrency


45. If x has the value 5.1356, x.toFixed(3) returns what value?a. 5.13 c. $5.13b. $5.135 d. 5.136


46. The ____ method returns a text string with n significant digits to the left or right of the decimal point.a. toPrecision c. toExponentialb. toFixed d. toDigits


47. Given the following code:var result = 10/"A";document.write(result);

What value will be displayed?a. N/A c. NaNb. NonN d. infinity


48. 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)


49. When displaying the value 5.78912, JavaScript shows ____ digits by default.a. 0 c. 4b. 2 d. 6


50. 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


51. ____ converts a text string, myString, to a number with decimal places.a. parseText c. parseDecimalb. parseInt d. parseFloat


52. 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


53. The general format of the conditional operator is ____.a. (condition) : falseValue ? trueValue c. (condition) ? falseValue : trueValueb. (condition) : trueValue : falseValue d. (condition) ? trueValue : falseValue


54. The ____ comparison operator returns true if variables are equal.a. != c. >=b. == d. <=


55. The ____ comparison operator returns true if variables are not equal.a. ~= c. !=b. == d. ++


56. The ____ logical operator returns true when both expressions are true.a. || c. ==b. | d. &&


57. The ____ logical operator returns true when either expression is true.a. || c. ==b. | d. &&


58. The ____ logical operator returns true if the expression is false and false if the expression is true.a. || c. &&b. ! d. ==


59. 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;


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. 10b. a.m., 9 d. a.m., 8


61. A(n) ____ command runs after a specific amount of time.a. time-delayed c. delayedb. interval-run d. time-interval


62. 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);


63. 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);"


64. 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);


65. 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();


66. A(n) ____ command instructs a browser to run the same command repeatedly.a. timed-interval c. time-delayed

b. interval-run d. delayed


67. 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();


68. 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);


69. 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


70. To clear all commands set to repeat, you use ____.a. clearTimeout() c. clearDelay()b. clearRepeat() d. clearInterval()


Case-Based Critical Thinking Questions

Case 2-1Legend Films is planning to create a page that will allow users to email 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. Arithmeticb. 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 fileb. 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 ____.

a. asp c. jsb. script d. php



Case 2-2Carol 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. setTimeoutb. 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. onunloadb. onexit d. onload


76. The goodbye message will most likely involve using the ____ event.a. onenter c. onunloadb. onexit d. onload


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 eventb. external file d. onload event

ANS: A PTS: 1 REF: JVS 58 TOP: Critical Thinking


Case 2-3Betty'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. onclickb. onkeypress d. onmouseout


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();

c. document.finalAmount.results.value = calcTotal();d. document.results.finalAmount.value = calcTotal();


80. Betty gets complaints that customers are seeing NaN in certain places. What function can help her stop that from happening?a. isFiN c. isNaNb. isNumber d. isFinite


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 56

2. The ____________________ event handler executes when the mouse button is released.

ANS: onmouseup

PTS: 1 REF: JVS 57

3. A(n) ____________________ object is an object containing date information.

ANS: date

PTS: 1 REF: JVS 59

4. The keyword ____________________ indicates that you are creating a new object.

ANS: new

PTS: 1 REF: JVS 59

5. To extract the day of the month from a given date object, JavaScript provides the ____________________ method.

ANS:getDate()getDate

PTS: 1 REF: JVS 60

6. The ____________________ method exists for extracting the value of the current month from a date object.

ANS:getMonth()getMonth

PTS: 1 REF: JVS 61

7. The ____________________ method can be used to set the time of a Date object in milliseconds since January 1, 1970.

ANS:setTime()setTime

PTS: 1 REF: JVS 63

8. A(n) ____________________ is a symbol used to act upon an item or a variable within a JavaScript expression.

ANS: operator

PTS: 1 REF: JVS 66

9. The + operator belongs to a group of operators called ____________________ operators, which perform simple mathematical calculations.

ANS: arithmetic

PTS: 1 REF: JVS 66

10. The ____________________ operator can be used to increase the value of a variable by 1.

ANS:increment++

PTS: 1 REF: JVS 67

11. To subtract one from a variable named count before using it, you should use the ____________________ operator.

ANS:decrement--

PTS: 1 REF: JVS 67

12. In "y = ++x;" , x is ____________________ before y is assigned a value.

ANS: incremented

PTS: 1 REF: JVS 68

13. When subtracting one date from another, the answer is measured in ____________________.

ANS: milliseconds

PTS: 1 REF: JVS 70

14. A(n) ____________________ statement is one that runs only when specific conditions are met.

ANS: conditional

PTS: 1 REF: JVS 83

15. A(n) ____________________ operator compares the value of one element with that of another.

ANS: comparison

PTS: 1 REF: JVS 83

16. " x = y== 2 ? 45 : 50;" is an example of a(n) ____________________.

ANS:conditionalconditional operator

PTS: 1 REF: JVS 83

17. The ____________________ operator returns true if two expressions are true.

ANS: &&

PTS: 1 REF: JVS 84

18. If x has the value of false, then !x returns ____________________.

ANS: true

PTS: 1 REF: JVS 84

19. A(n) ____________________ command runs once after a specified amount of time passes.

ANS: time-delayed

PTS: 1 REF: JVS 88

20. 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 operatorb. negation operator h. logical operatorc. conditional operator i. comparison operatord. date object j. Math object

e. unary operator k. increment operatorf. date method l. event handler

1. Allows you to connect several expressions2. A ternary operator that executes a test3. Has methods for rounding numbers4. Requires two operands5. Used to create expressions that have true or false values6. Perform simple calculations7. Changes an item's sign8. Can be placed before or after an operand9. Requires one operand

10. Tells browsers what code to run11. Retrieves information from a date object12. Created using Date();

1. ANS: H PTS: 1 REF: JVS 842. ANS: C PTS: 1 REF: JVS 833. ANS: J PTS: 1 REF: JVS 724. ANS: G PTS: 1 REF: JVS 675. ANS: I PTS: 1 REF: JVS 836. ANS: A PTS: 1 REF: JVS 667. ANS: B PTS: 1 REF: JVS 688. ANS: K PTS: 1 REF: JVS 679. ANS: E PTS: 1 REF: JVS 67

10. ANS: L PTS: 1 REF: JVS 5611. ANS: F PTS: 1 REF: JVS 6012. 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.

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

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