Jquery 1.4: Ajax Functions

Front 1

define XHR

Back 1

Refers to XMLHttpRequest, a method implemented by standards compliant browsers to receive asynchronous requests in JavaScript

Front 2

define AJAX

Back 2

Asynchronous JavaScript and XML

Front 3

where did AJAX get its origins?

Back 3

As part of Outlook Web Access, Microsoft released an ActiveX control in 1998. It wasn't made popular until Google used it in 2005

Front 4

Describe difference between AJAX implementations in IE 6 and 7

Back 4

IE 7 uses a wrapper that is compliant with the XHR standard, instead of IE 6's active X call.

Front 5

(true or false) jQuery uses the new IE 7 wrapper for XHR

Back 5

As of 1.4, this is false; jQuery feels that the wrapper in IE 7 is buggy, so it goes straight to the source

Front 6

Define the XHR method: abort() method

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cancels currently executing request

Front 7

Define the XHR method: getAllResponseHeaders()

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returns string containing the names and values of all response headers

Front 8

Define the XHR method: getResponseHeader(name)

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returns value of one header

Front 9

Define the XHR method: open(method,url,async,user,pass)

Back 9

Sets the HTTP request method (GET or POST) and URL to be requested. Other parms are optional

Front 10

What is the purpose of async in this method: open(method,url,async)

Back 10

async is true by default, is false, the request is much like normal HTTP (synchronous, not loaded in background)

Front 11

Define the XHR method: send(content)

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initiates XHR request with 'content' as the body of the request

Front 12

Define the XHR method: setRequestHeader(key, value)

Back 12

sets a request header used in the XHR request

Front 13

Define the XHR property: onreadystatechange

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The event handler invoked when the request is returned or fails.

Front 14

Define the XHR property: readyState

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Integer representing current state:
0 - UNSENT
1 - OPENED
2 - HEADERS_RECEIVED
3 - LOADING
4 - DONE

Front 15

Define the XHR property: responseText

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body content returned in the response

Front 16

Define the XHR property: responseXML

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if the body was XML content, this is the DOM structure for that content

Front 17

Define the XHR property: status

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HTTP response code from the server: 200/success; 400/not found

Front 18

Define the XHR property: statusText

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description of the HTTP response code

Front 19

when using ajax queries, what do status codes 200-299 represent?

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success (these are actually the HTTP request codes)

Front 20

when using ajax queries, what do status codes of 300 or above represent?

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failures (these are actually the HTTP request codes)

Front 21

explain the purpose of the $(...).load() method

Back 21

sends an XHR request via get or post, depending on the arguments passed, loads the results into each element of the wrapped set

Front 22

explain the params argument in $(...).load(url, params, callback) and its effect on the request type

Back 22

an optional string, array, or object

if omitted, GET method is used

as a string, it is a query string and GET is used

as an array, each element is an object formatted: {name: "name", value: "the val} and POST is called

as an object, POST is called

Front 23

explain the callback argument in $(...).load(url, params, callback)

Back 23

optional

It receives two arguments: response text (i.e. 'success'), and the XHR instance

invoked once for each element in the wrapped set with 'this' equal to DOM element being iterated

Front 24

explain how to force $('...').load() method to use the GET method when passing arguments

Back 24

place the arguments into the URL parameter using encodeURIComponent() or $.param()

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explain how to filter the results of $('...).load() so that only div elements are inserted into the wrapped set

Back 25

put a space and a selector onto the url, for example:

$('...').load("/xhr.php div");

Front 26

what method can be used to prepare form data for use as an argument to jQuery XHR methods?

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$(...).serialize()

Any form elements in the wrapped set are used.

If forms exist in the wrapped set, all their elements are used.

Front 27

explain the purpose of $(...).serializeArray()

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returns form elements as array of {name: ..., value: ...} objects suitable for use with jQuery XHR methods

Front 28

what jQuery utility method executes a GET request?

Back 28

$.get(...)

Front 29

what are the valid data types for parms in:

$.get(url, parms, callback, type)

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query string, array of name/value objects, or JS object

Front 30

explain the callback parm in:

$.get(url, parms, callback, type)

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method called when $.get() returns

Front 31

explain possible values of the dataType property passed to the $.ajax() utility method

Hint: It is the same as the type argument in $.get(url, parms, callback, type)

Back 31

xml, html, json, jsonp, script, text

Front 32

When setting properties for $.ajax() method, explain the dataType of 'xml'

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returns XML DOM object parsed from the returned text body

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When setting properties for $.ajax() method, explain the dataType of 'jsonp'

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similar to json, except remote scripting is allowed

Front 34

What happens to <script> tags when setting the dataType for jQuery's $.ajax() method to 'html'?

Back 34

they are evaluated when inserted into the DOM

Front 35

what method returns AJAX call in JSON format?

Back 35

$.getJSON(url, parameters, callback)

returned JSON object is passed to callback

Front 36

what type of HTTP request does $.getJSON() utilize?

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GET request

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what is the purpose of callback in $.getJSON(url, parms, callback)

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receives the JSON object returned

Front 38

what jQuery utility creates an HTTP request with type POST?

Back 38

$.post()

Front 39

what jQuery utility method provides advanced control over execution of XHR requests?

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$.ajax(options)

Front 40

explain the $.ajax() option: type

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the HTTP request type (GET or POST)

defaults to GET

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explain the $.ajax() option: data

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a query string, JS object, or array of name/value objects

Passed in the url for GET requests, as part of body for POST requests.

Front 42

explain the $.ajax() option: dataType

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Defines the format of the returned data. If omitted, jQuery will guess based on returned content

One of xml, html, json, jsonp, script, or text

Front 43

when using $.ajax(), the property dataType can be set to 'script' - what does this do?

Back 43

executes the returned value as JS statements, then passes it to the callback (if any)

Front 44

explain the $.ajax() option: cache

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if false, ensures response is not cached by the browser

Front 45

in what cases does the $.ajax() cache option default to true?

Back 45

All cases except when dataType is set to jsonp or script

Front 46

explain the $.ajax() option: context

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overrides 'this', setting the context for all callback invocations

Front 47

explain the $.ajax() option: timeout

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milliseconds until timeout, if expired, request is aborted and error callback is invoked (if defined)

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explain the $.ajax() option: global

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if false, disables triggering of jQuery global ajax events, defaults to true (enabled)

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explain the $.ajax() option: contentType

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content type specified in HTTP request, defaults to application/x-www-form-urlencoded (default for form submissions)

Front 50

explain the $.ajax() option: success

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a function invoked if request succeeds

first parm is request body, second is the text 'success', third is XHR instance

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explain the $.ajax() option: error

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a function invoked if request fails

first parm is request body, second is the text 'error|timeout|notmodified|parseerror', third is XHR instance

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explain the $.ajax() option: complete

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called after error or success callbacks (if they are defined), receives XHR instance and status string

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explain the $.ajax() option: beforeSend

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called before initiating request, receives XHR instance as param

returning false from this callback cancels the request

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explain the $.ajax() option: async

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defaults to true, if set to false, synchronous request is sent (blocks browser activity just like a page load)

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explain the $.ajax() option: processData

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if false, data passed is not processed into a url-encoded format

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explain the $.ajax() option: dataFilter

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callback function called to filter result data, passed the raw result data and dataType value, must return the "sanitized" data

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explain the $.ajax() option: ifModified

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if true, request succeeds only if response content has not changed since last request, according to the Last-Modified header, defaults to false

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explain the $.ajax() option: jsonp

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overrides the default jsonp callback parameter

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explain the $.ajax() option: scriptCharset

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the character set used for script and jsonp requests when remote and local have diff charsets

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explain the $.ajax() option: xhr

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a callback used to provide custom implementation of the XHR method

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explain the $.ajax() option: traditional

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if true, traditional parameter stylization is used (see $.param())

Front 62

how can one set a default list of ajax options instead of passing them each time to $.ajax()?

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$.ajaxSetup(options)

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(true or false) defaults set with $.ajaxSetup() also affect the $(...).load() method

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false, additionally, overriding the type option has no effect on $.get() and $.post() util methods (they igonore it)

Front 64

What method is used to establish global listeners for Ajax requests?

Back 64

$.bind(), just like any other listeners in jQuery

Front 65

What are the Ajax related events that can be monitored?

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ajaxStart, ajaxSend, ajaxSuccess, ajaxError, ajaxStop, and ajaxComplete

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What arguments are given to the listeners for ajaxStart events?

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none

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What arguments are given to the listeners for beforeSend events?

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the XHR instance

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What happens if the listener for beforeSend returns false?

Back 68

the XHR is canceled

Front 69

What arguments are given to the listeners for ajaxSend events?

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jQuery.Event, XHR instance, and options passed to $.ajax()

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What arguments are given to the listeners for ajaxSuccess events?

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jQuery.Event, XHR instance, and options passed to $.ajax()

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What arguments are given to the listeners for ajaxComplete events?

Back 71

jQuery.Event, XHR instance, and options passed to $.ajax()

Front 72

What ajax event is always triggered, even for synchronous events?

Back 72

ajaxComplete

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What arguments are given to the listeners for ajaxError

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jQuery.Event, XHR instance, options passed to $.ajax(), and the error as an optional 4th parameter