SOEN 287

A: Yes, No

• A: Java and JS are only related through syntax. - JS is dynamically typed
• - Objects are treated very differently

A: Transfers load from often over-loaded servers to under-loaded clients

• A:
• Implicit
• - external file by adding 'src' attribute
• - Good because it hides script from users and older incompatible browsers
• - Good because it seperates two different notations

• Explicit
• - directly embedded in script
• - Bad as it mixes notations
• - Bad as it is difficult for different 'expert' to work on same doc
• - Can be convenient in certain cases (like very little JS)

• A: - It does not support inheritance or polymorphism. It is considered more of an 'object-based language'.
• - Objects in JS are descendent from the root Object, and are a collection of data properties

A: <script> <!-- JavaScript code //--></script>

A: JS tries to implicitly insert them where they make sense, but sometimes misses and cuts statements off at points where they could be standalone expressions, but really should include the rest of the line. Thus best to specify them yourself and to place statements all on one line when possible.

• A: Primitives: Number, Boolen, String, Undefined, Null
• Wrappers: Number, Boolean, String

A: None, just be consistent. Also, when inserting the same type of quote within the string, it needs to be escaped. In other words, you need to escape singles within a single, and doubles within a double, but not a double within a single and vice versa..

A: isNaN()

• A: String - TRUE, unless it is EMPTY or ZERO ("0"(but not "0.0"))
• Number - TRUE, unless it is ZERO
• NaN - FALSE
• Undefined - FALSE

• Relational expressions:
• String and Number - Attempts to coerce string to number
• Bool and NonBool - Coerces boolean to number; 0 or 1

• Conditional expression:
• If a boolean is used in a conditional expression: - It is TRUE, unless it is NULL or UNDEFINED

• Number: "number"
• String: "string"
• Boolean: "boolean"
• Object or Null: "null"
• Undefined: "undefined"
• Function: "function"

A: It will go by the lest variable first. So if the left variable is a string, the operator '+' and the righ a number, it will corece the right to a string and concatenate. However if the orders are reversed, it will try to add first.

• A: 1. Use Array() contructor
• var arr1 = new Array(1, 2, “three”, “four”);
• // Length 4 and initialized to values

• var arr2 = new Array(100);
• // Length 100, uninitialized

• 2. Use literal array values var arr3 = [1, 2, “three”, “four”];
• // Equivalent to arr1

A: join() will combine the elements of an array into a string. Seperator is comma by default, or whatever param is passed

split() will split a string into an array. Seperator is space by default, or whatever param is passed

A: arr1.sort(); // Coerces elements to strings and sort lexicographically

A: pop and push deal with end of array, shift and unshift with beginning

A: the concat() method. Pass the value to add as an argument

A: They should be defined before they are used. This way they are defined before any calls from the body.

A: Any variable declared outside of functions has global scope; there is not such thing as block-scope. An array defined within a function definition has local-scope, and takes precedence of any global variableof the same name.

A: Arguments passed are placed in an implicit arguments array, where they can be accessed like in any other array. It is particularly useful when dealing with a variable number of parameters (can use arg-array in a loop or something).

• search() - returns index of matched pattern
• match() - returns matches in an array
• replace(pat,rep) - replaces pattern (pat) with replacement (rep)
• split(sep) - seperates string into an array at seperator (sep)

A: The pattern in parantheses is remembered. Can be "forgotten" by including '?:' e.g. (?:x) will match x but not store it in matches array

• '.' Matches any characeter except newline
• [ ... ] Can define classes of characters to search
• [^ ... ] Inverses the specified set, so everying “except” these.
• \d or [0-9] A digit
• \D or [^0-9] Not a digit
• \w or [A-Za-z_0-9] An alphanumeric word character
• \W or [^A-Za-z_0-9] Not a word character
• \s or [ \r\t\n\f] A white space character
• \S or [^ \r\t\n\f] Not a white space character

• A: To specify how many repitions of the pattern should be found.
• - {n}: strictly n reptitions
• - {n,m}: At least n, but no more than m repitions
• - {n,}: At least n repitions

• * - zero or more
• + - one or more
• ? - one or none

A: In []s, inverses the pattern. Outside [] means pattern must be first thing in search string.

• i - ignore case
• x - ignore whitespace
• g - global, meaning search entre string for all matches, not just one

• for(var prop in arr1){
• document.write(arr1[prop] + "<br />");
• }

A: It can be used to SET lenth. If length is reset, undefined elements have value "undefined", and elements no longer in length are deleted (i think).

A: NO. Unused formal parameters are unbound, and excess actual parameters are ignored.

• - The DOM is an abstract model that defines the interface between HTML documents and application programs—an API
• - Documents in the DOM have a treelike structure
• - A language that supports the DOM must have a binding to the DOM constructs

A: document.form[i].elements[j]; // Forms and Elements are placed into implicit arrays (properties of document object) based on their order

A: Name attribute not accepted in xhtml. Best to use document.getElementById('id');

• - An event is an object (notification) created by the browser to notify that something specific has occured.
• - An event handler is a script that is implicitly executed in response to the appearance of an event
• - The process of connecting an event handler to an event is called registration

Method 1. Assign event handler to attribute By assigning the event handler script to an event tag attribute

• Method 2. Assign event handler to property
• - Assign the address of the handler function to the event property of the JavaScript object associated with the HTML element.
• - The registration must follow both the handler function and the HTML form

A: Saves sever some time and effort. It is often over-loaded whilst client is not.

• A:
• Copy – when it encounters markup code, it simply copies it to the output file as is

Interpret – when it encounters php script, it interprets it and send any output to the output file. Thus the output should be in HTML.

A: Interger, Double, String, Boolean, array, object, null, resource

A: When using singles, variables and excape sequences are not interpolated.

Integer: FALSE if ZERO, TRUE otherwise

String: FALSE if “” or “0”, TRUE otherwise (including “0.0”)

Double: Only 0.0 exactly evaluates to FALSE (again, this isn't the same as the string “0.0”, which evaluates to TRUE.

A: Strings are coerced to numbers if they begin with a number, otherwise result in zero. If the initial number is a double (ie contains a decimal point or 'e' notation, it can be coerced as a double). Non-numeric characters following the number are ignored.

• Explicit type conversion can be done using C-like notation: (int) $sum;
• or calling one of the intval, doubleval or strval function: intval(sum);
• or also by using the settype function: settype($sum, “integer”);

A: Essentially a combination of all sorts of arrays. Stored as key-value pairs, so can behave like traditional array, or hash-list

• 1. Assigning a value to a subscripted variable that was previously not an array creates the array: Ex: $list[0] = 17;
• // $list is not an array with one element: 0 => 17

If empty brackets are furnished, a key is implicitly added. This will be one greater than the previous elements key if it is a number, or '0' if no numeric key has been previously used in the array. Furthermore, elements of an array need not be of the same type.

• 2. Using the array contruct:
• Ex: $list2 = array(17, 24, 45, 91);
• // 0 =>17, 1 => 24, 2 => 45, 3 => 91

• $list3 = array(1 =>17, 2 => 24, 3 => 45, “woah” => 91);
• // Can specify keys

A: explode(" ", $arr) and implode(" ", $arr) // Seperator a space here, but can be specified to whatever

• A: foreach($array as $value)
• or
• foreach($array as $key => $value)

• sort($array) - Sorts values and replaces keys with 0,1,2...
• asort($array) - Sort values, but keeps original keys
• ksort($array) - Sorts by keys rather than values
• rsort, arsort and krsort do the same, but in reverse.

• Functions need not appear in a document before they are called, so their placement is somewhat irrelevant.
• Functions can not be overloaded.
• Functions are not case sensitive.
• Much like in JS, number of params is not checked; excess is ignored, too few means remaining formal are unbound

A: Add an ampersand (&) before the variable passed in the function.

A: The default scope of functions is local, thus hiding any variables of the same name outside of the function. If you want the scope of a variable to be global, you must add this declaration outside of the function.

preg_match(pattern_to_match, $str_to_match); // returns boolean and

preg_split(pattern_to_match, $str_to_match); // returns array of split string

A: Depending on method (POST or GET), all form elements will be stored in implicit array ($_POST or $_GET) by their name, and their values can be accessed from there.

• - Cookies are returned only to the server that created them
• - Cookies can be used to determine usage patterns that might not otherwise be ascertained by a server
• - Browsers generally allow users to limit how cookies are used
• - Browsers usually allow users to remove all cookies currently stored by the browser
• - Systems that depend on cookies will fail if the browser refuses to store them
• - Not all clients support or accept cookies
• - Cookies can be disabled
• - This is similar to the client-side validation using JavaScript
• - According to the cookie specification, no cookie can exceed 4 KB in size,
• - Only 20 cookies are allowed per domain
• - A total of 300 cookies can be stored on the client side

A cookie is one means of tracking customer data, which can be useful for a variety of reasons, like cart-tracking or personlization of the webpage. The main problem with cookies is that they can be blocked or disabled by the user, making them useless. Otherwise, they are sent to the server where they can be processed and used to send back specific information to the client.

A session is the time span during which a browser interacts with particular server. A session begins when a browser connects to the server and ends when either the browser is closed or the server terminates the session due to inactivity (usually default is something like 30min).

• Similarities with cookies:
• - Hold information about one single user
• - Pass information from one page to another in your application

• Differences from cookies:
• - Store the information at the server side instead of the client side
• - Session information is deleted after the user has left the website (although permanent storage is possible)

• For session tracking, PHP creates and maintains a session tracking id
• - The session id is either stored in a cookie or is propagated in the URL
• - Create the id with a call to session_start() with no parameters
• - To use cookie-based sessions, session_start() must be called before outputting anything to the browser
• - To store and retrieve session variables, use the PHP $_SESSION variable

• Delete some session data using unset( ) function
• <?php
• unset($_SESSION['views']);
• ?>

• Completely destroy the session by calling the session_destroy() function
• <?php
• session_destroy();
• ?>

• - session_destroy() destroys all of the data associated with the current session
• - It does not unset any of the global variables associated with the session, or unset the session cookie.
• - To use the session variables again, session_start() has to be called