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Javascript 2 > Terms > Flashcards

Terms Flashcards

1
Q

What type of language is JavaScript?

A

It is a scripting language.

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2
Q

JavaScript is a scripting language. What is a scripting language?

A

A scripting language is a lightweight programming language.

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3
Q

What would be the result of the following code?

<h1>This is a heading</h1>

<p>This is a paragraph.</p>

A

It will write what is between the <h1> and <p> tags to the browser screen formated accordingly to the respective HTML tags

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4
Q

What happens is you use:

document.write

After the document has loaded?

A

The whole document will be overwritten. Only use in the HTML output.

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5
Q

The alert() function is not much used in JavaScript, however it is useful for…?

A

It is often quite handy for trying out code.

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6
Q

What will this code do?

<p>

JavaScript can change the content of an HTML element.

</p>

A

It will change the text between the <p> tags to the content in quotes after x.innerHTML

Hello JavaScript!

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7
Q

This piece of code tells the computer to do what?

x=document.getElementById(“demo”);

A

Find the Element

(“demo”);

document.getElementById(“some id”)

The “Id” could be anything else.

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8
Q

This piece of code tells the computer to do what?

x.innerHTML=”Hello JavaScript!”;

A

Change the content of the x variable to Hello JavaScript!

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9
Q

What is the difference between JavaScript and Java ?

A

They are two completely different languages, in both concept and design.
Java (invented by Sun) is a more complex programming language in the same category as C.

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10
Q

What is the official name of the JavaScript standard ?

A

ECMA-262

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11
Q

Who invented JavaScript ?

A

Brendan Eich

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12
Q

In what year and what browser did JavaScript first appear ?

A

1995

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13
Q

In what year did the ECMA (a standard association) adopt JavaScript ?

A

1997

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14
Q

Who is the ECMA ?

A

European Computer Manufacturers Association

now the ECMA International

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15
Q

In an HTML document JavaScript must be placed between which tag ?

A
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16
Q

In what section of an HTML document can JavaScript be placed ?

A

The or the sections.

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17
Q

JavaScript can be placed in which part(s) of an HTML document ?

A

The or the sections.

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18
Q

It is common practice to place all JavaScript where in an HTML document ?

A

All in the section or at the end of the section, this way it is all in one place and does not interfere with the page content.

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19
Q

What does the following code do?

<!DOCTYPE html>

A

Links the “myScript.js” JavaScript file to the HTML document. Example of an External JavaScript file.

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20
Q

Is there something wrong with this file named:

myScript.js

A

External scripts cannot contain

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21
Q

What is JavaScript typically used for in regard to HTML documents ?

A

To manipulate HTML elements.

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22
Q

How do you access an HTML element from JavaScript

and what attribute do you use in the HTML?

A

To use the document.getElementById(“id”) method.

Use the id=” “ attribute to identify the HTML element:

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23
Q

JavaScript is a sequence of __________ to be executed by the browser.

A

statements

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24
Q

JavaScript statements are ________ to the browser.

A

commands

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25
Q

What is at the end of all JavaScript statements to separate each one from the next?

A

A semicolon ;

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26
Q

Is the semicolon at the end of each statement necessary?

A

No, it’s optional

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27
Q

JavaScript statements are grouped together in ______.

A

blocks

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28
Q

Blocks of JavaScript start and end with what?

A

Start with a left curly bracket and end with a right curly bracket.

Ex.

{

statement;

statement;

}

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29
Q

What is the purpose of grouping JavaScript statements together in blocks?

A

So that they execute together.

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30
Q

Is JavaScript case sensitive?

A

Yes

Ex.

getElementById is not the same as getElementbyId (the first one is correct)

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31
Q

Which one is correct:

var name="Hege";
var name = "Hege";
A

Both… JavaScript ignores extra spaces. You can add white space to your script to make it more readable.

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32
Q

You can break up a code line within a text string using what?

A

A backslash \

Ex.

document.write(“Hello \
World!”);

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33
Q

What is the difference in how a scripting language (JavaScript) is executed verses how a traditional programming language is executed?

A

Scripting code is executed line by line while the browser reads it. With traditional programming, all the code has to be compiled before it can be executed.

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34
Q

How do you insert a single line comment in JavaScript?

A

Two forward slashes

Ex.

// This is a single line comment

// This is another one

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35
Q

How do you insert a multi-line comment in JavaScript?

A

Comment starts with a forward slash and an asterisk and ends with an asterisk and a forward slash.

Ex.

/* This is an example of a multi-line comment as it should be formated in JavaScript code. */

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36
Q

Why would you use comments to prevent certian lines of code or statements from being executed?

A

Can be useful for debugging.

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37
Q

Think of variables as __________ for storing data.

A

containers

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38
Q

Variable can have shortVariable can have short names (like x and y) or more descriptive names (age, sum, totalvolume).

A

True

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39
Q

True or False

Variable names can begin with a letter or a number.

A

False

Variable names must begin with a letter.

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40
Q

Besides a letter, variable names can begin with what two symbols

A

Variable names can also begin with $ and _

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41
Q

Are JavaScript variables case sensitive?

A

Yes

Variable names are case sensitive (y and Y are different variables)

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42
Q

Besides numbers JavaScript variable can also hold ________.

A

Other types of data, like text values (name=”John Doe”).

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43
Q

In JavaScript a text variable like “John Doe” is called a ______.

A

string

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44
Q

When you assign a text value to a variable what do you put around it?

A

Single or double quotation marks.

Ex.

var name=’john doe’

 OR

var name2=”jane doe”

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45
Q

Creating a variable in JavaScript is most often referred to as _________ a variable.

A

declaring

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46
Q

What keyword do you use in JavaScript to declare a variable?

A

The var keyword.

Ex.

var name=”john doe”;

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47
Q

What is the case if you declare a variable with no value?

Ex.

var carname;

A

The variable is empty

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48
Q

It’s a good programming practice to declare all the variables where?

A

All in one place at the beginning of your code.

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49
Q

You can declare multiple variables in one statement separated by what?

A

A comma

Ex.

var name=”Doe”, age=30, job=”carpenter”;

  OR Multi-line
var name="Doe",
age=30,
job="carpenter";
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50
Q

Variables declared without a value will have the value _________.

A

undefined

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51
Q

Undefined or empty variables may receive a value later by what means.

A

The result of a calculation or user input.

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52
Q

What will happen if you re-declare a variable?

Ex.

var carname="Volvo"; 
var carname;
A

The variable will still retain the value “Volvo”

53
Q

What do you use to perform arithmetic with variables?

A

Operators like + , - , =

54
Q

JavaScript has dynamic data types. What does this mean?

A

Means that the same variable can be used as different types.

Ex.

var x                // Now x is undefined
var x = 5;           // Now x is a Number
var x = "John";      // Now x is a String
55
Q

Name 7 JavaScript data types.

A

number, string, boolean, array, object, null, undefined

56
Q

What is a JavaScript string?

A

A variable which stores a series of characters like “John Doe”.

57
Q

Can you use quotes inside a string?

A

Yes, as long as they don’t match the quotes surrounding the string.

Ex.

var answer="It's alright";
var answer="He is called 'Johnny'";
var answer='He is called "Johnny"';
58
Q

What is a good way to write extra large or small numbers in JavaScript variables.

A

Using scientific (exponential) notation.

Ex.

var y=123e5;      // 12300000
var z=123e-5;     // 0.00123
59
Q

What are the only two values that a boolean can have?

A

true or false

60
Q

Booleans are often used for what?

A

Conditional testing

61
Q

What is a JavaScript array?

A

A list of values for a variable.

Ex.

var cars=new Array();
cars[0]="Saab";
cars[1]="Volvo";
cars[2]="BMW";
 OR a condensed array

var cars=new Array(“Saab”,”Volvo”,”BMW”);

 OR a literal array

var cars=[“Saab”,”Volvo”,”BMW”];

62
Q

An array index in numbered in what manner?

A

They are zero based, meaning that the first item is [0], the second [1], and so on.

63
Q

How is a JavaScript object delimited?

A

With curly braces.

Ex.

var person={firstname:”John”, lastname:”Doe”, id:5566};

64
Q

Inside the curly braces the objects properties are defined as ____ and _____.

A

( name : value )

65
Q

The properties in an object are separated by what?

A

A comma.

Ex.

var person={firstname:”John”, lastname:”Doe”, id:5566};

 OR
var person={
firstname : "John",
lastname  : "Doe",
id        :  5566
};
66
Q

What are 2 way you can address an object?

A

name=person.lastname;

name=person[“lastname”];

67
Q

Variables can be emptied by setting the value to what?

A

null

Ex.

cars=null;
person=null;

68
Q

When you declare a new variable you can declare its type by using what keyword?

A

The “new” keyword.

Ex.

var carname=new String;
var x=      new Number;
var y=      new Boolean;
var cars=   new Array;
var person= new Object;
69
Q

JavaScript variables are all _______.

A

objects

When you declare a variable you create a new object.

70
Q

In JavaScript, an object is data, with __________ and _______.

A

properties and methods

71
Q

Give an example of object properties.

A

car. name=Fiat
car. model=500
car. weight=850kg
car. color=white

72
Q

Give an example of object methods.

A

car. start()
car. drive()
car. brake()

73
Q

Properties are ______ associated with an object.

A

values

74
Q

Methods are _______ that can be performed on an object.

A

actions

75
Q

In object oriented languages, properties and methods are often called ______ _______.

A

object members

76
Q

Almost everything in JavaScript is a ______.

A

object

Strings, Dates, Arrays, Functions

77
Q

What is this example doing?

person=new Object();

person. firstname=”John”;
person. lastname=”Doe”;
person. age=50;
person. eyecolor=”blue”;

A

Creating a new object named “person” and assigning 4 properties to it.

78
Q

What is the syntax for accessing the property of an object?

A

objectName.propertyName

79
Q

What will the value of x be after the execution of this code:

var message="Hello World!";
var x=message.length;
A

12

80
Q

What is the syntax for calling a method on an object?

A

objectName.methodName()

81
Q

What will be the result of executing the following code?

var message="Hello world!";
var x=message.toUpperCase();
A

HELLO WORLD!

82
Q

It is common in object oriented languages to use _____ ____ function names. Give example.

A

camel-case

someMethod() instead of some_method()

83
Q

What is a JavaScript function?

A

A block of code that will be executed when “someone” calls on it.

84
Q

A function is written as a code block inside what and preceeded by what.

A

curly braces { } and preceeded by the function keyword

Ex.

function functionname()
{
some code to be executed
}
85
Q

A function can be called directly when an event occurs such as.

A

A user clicks a button.

86
Q

A function can be called from where in JavaScript code?

A

Anywhere

87
Q

When you call a function, you can pass along some values to it, these values are called _________ or __________.

A

arguments or parameters

88
Q

How many arguments can you assign to a function?

A

You can send as many arguments as you like, separated by commas (,)

Ex.

myFunction(argument1,argument2)

89
Q

The variables and arguments must be in ________ order.

A

expected

90
Q

What would the following JavaScript do when run ?

Ex.

“Example”.length

A

Give an output of ‘ 7 ‘

In other words the characters in the string would be counted (including spaces) and provide a numerical output.

91
Q

What would be the output of this example ?

“Example two”.length * 2

A

22

92
Q

What will this example do ?

confirm(“This Example”);

A

It will bring up a ‘ confirmation ‘ box with the words ‘ This Example” with the option buttons of Ok or Cancel.

93
Q

What will this example do ?

prompt(“What is your name?”);

A

It will bring up a box asking the question ‘ What is your name? ‘ and provide a text entry field for the user to answer in.

94
Q

Name three common data types.

A

Numbers

Strings

Booleans

95
Q

What are the only two possible values for booleans ?

A

True or False

96
Q

Who is the boolean data type named after?

A

George Boole

97
Q

What does console.log() do ?

A

It will take whatever is inside the parentheses and log it to the console below your code.

This is commonly called printing out.

98
Q

Name 5 comparison operators.

A

> Greater than
< Less than
= Greater than or equal to
=== Equal to

99
Q

What is an if statement or a conditional statement?

A

The usage of comparisons plus booleans to decide whether a block of code should run.

100
Q

What is the basic syntax of a function in JavaScript?

A

function name (parameter) {//code;}

101
Q

What does D.R.Y. stand for in programming?

A

Don’t Repeat Yourself

102
Q

Any time you find yourself typing the same thing, but modifying only one small part, you can probably use what?

A

A function

103
Q

Can functions have more than one parameter?

A

Yes

104
Q

What is the basic syntax of a for loop?

A

for (i=0; i<11; i++) {//code;}
Basically, while the condition above is true it will run the code in curly brackets and increment by 1 each time until i is no longer less than 11.

105
Q

ame two ways to increment a number up by “1”

A

Provided the variable is i

i + 1

i++

106
Q

Name two ways to decrement a number by “1”

A

i - 1

i–

107
Q

What is the syntax for incrementing or decrementing by any numerical value ?

A

Provided i is the variable and x is the numerical level of increment or decrement.

i += x

i -= x

108
Q

What is the basic syntax of an array ?

A

var array = [];

Note the square brackets

109
Q

What does Math.random() do in JavaScript ?

A

The computer chooses a random number between 0 and 1

Ex.

  1. 0138295739957
  2. 9845837659374
110
Q

What is a while loop ideal for?

A

When you want to use a loop, but you don’t know how many times you’ll have to execute that loop.

111
Q

What is the basic syntax of a while loop?

A

while(condition){ // Do something! }

112
Q

What do you put at the end of a long string to wrap to the next line?

A

a backslash ‘ \ ‘

Ex.

text =”This is a long string in the code \

      editor with a backslash at the \

      end of each line that wraps";
113
Q

What does /*jshint multistr:true */ do ?

A

It tells the console to stop worrying about our use of backslash characters for wrapping long lines of text.

114
Q

What is a for loop ideal for ?

A

Doing the same task over and over when you know ahead of time how many times you’ll have to repeat the loop.

115
Q

What is a ‘ do ‘ / ‘ while ‘ loop used for ?

A

When you want to make sure your loop runs at least one time no matter what. When this is the case, you want a modified while loop called ado/while loop.

116
Q

While loops will continue so long as ?

A

The loop will continue so long as the condition being evaluated is true.

117
Q

What is the basic syntax of a do / while loop?

A

var condition = false; do { console.log(“I’m printed once!”); } while(condition);

118
Q

The switch statement allows you to present a number of options called _____ ? then check an expression to see if it matches any of them. If there’s a match, the program will perform the action for the matching case; if there’s no match, it can execute a default option.

A

case(s)

119
Q

What is the basic syntax of a switch statement ?

A 
switch(expression) {
    case n:
        code block
        break;
    case n:
        code block
        break;
    default:
        default code block
}
120
Q

Name the 6 comparison operators.

A 
===  (equals)
!==   (not equal)
>      (greater than)
>=    (greater than or equal to) 
<      (less than)
<=    (less than or equal to)
121
Q

Name the 3 Boolean logical operators and define each.

A

&& (Logical AND, returns true if both expression1 and expression2 are true. Otherwise it returns false).
|| (Logical OR, returns true if expression3 or expression4 are true, or both are true. Otherwise it returns false).
! (Logical negation, returns the boolean that is the opposite of expression5).

122
Q

What is a heterogeneous array?

A

An array with a mixture of data types.

Ex.

var mix = [42, true, “towel”];

123
Q

What is a two-dimensional array ?

A

One or more arrays nested inside an array.

Ex.

var twoDimensional = [[1, 1], [1, 1]];

124
Q

What is an object?

A

Combinations of key-value pairs (like arrays), only their keys don’t have to be numbers like 0, 1, or 2: they can be strings and variables.

125
Q

What is the basic syntax of creating an object using object literal notation?

A

var myObj = { type: ‘fancy’, disposition: ‘sunny’ }; var emptyObj = {};

126
Q

What is the basic syntax of creating an object using object constructor ?

A 
var myObj = new Object();
You can add keys to your object after you've created it in two ways:

myObj[“name”] = “Charlie”;
myObj.name = “Charlie”;

127
Q

What are the two ways of creating an object ?

A

Literal object notation and object constructor

128
Q

What is the basic syntax of a for / in loop ?

A

for (var something in object) { // Do something }

Javascript 2 (1 decks)

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