Jquery 1.4: Utility Functions

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Purpose of $.support

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Provides flags for various functions to replace browser sniffing and ensure cross-browser functionality.

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Dose $.support.boxModel return true for IE?

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In quirksmode it returns false, in standards mode it returns true.

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define $.support.boxModel

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Set to true if user agent renders according to standards compliant box model.

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when is $.support.boxModel defined?

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on document ready

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define $.support.cssFloat

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true if cssFloat of elements style property is used by current browser

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define $.support.hrefNormalized

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true if obtaining href element attributes returns the value exactly as specified

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define $.support.htmlSerialize

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true if browser evaluates style sheets referenced by <link> elements when injected into the DOM via innerHTML

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define $.support.leadingWhitespace

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true if browser honors leading whitespace when text is inserted via innerHTML

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define $.support.noCloneEvent

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true if browser does not copy event handlers when event is cloned

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define $.support.objectAll

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true if getElementsByTagName() method returns all descendants when passed "*"

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define $.support.opacity

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true if browser correctly interprets standard CSS opacity property

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define $.support.scriptEval

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true if browser evaluates <script> blocks when they're injected via calls to appendChild() or createTextNode() methods

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define $.support.style

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true if the attribute for obtaining the inline style properties of an element is style

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define $.support.tbody

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true if browser doesn't automatically insert <tbody> elements into tables lacking them when injected via innerHTML

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list browsers for which all $.support variables return true

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All except for Internet Explorer, which always returns false for everything except boxModel

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purpose of $.browser object

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detects user agent types and sets flags for browser detection (DEPRECATED FUNCTION)

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list the flags set on $.browser

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msie - Internet Explorer
mozilla - Firefox and Camino (mozilla based)
safari - Safari, Chrome, OmniWeb (web-kit based)
opera - Opera
version - number of rendering engine for browser

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(true or false) $.browser.version is the version of the browser, such as IE 5.5

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false - it's the version of the rendering engine (which happens to be the same as the browser version in IE only)

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(true or false) $.browser.version represent the browser version for IE

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true - $.browser.version is the rendering engine number; however, in IE the rendering engine and browser have the same version number

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define $.noConflict(boolean)

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Restores control of $ identifier back to another library (such as Prototype), allowing multiple libraries on a single page.

If the boolean is set to true, then jQuery identifier is relinquished, too

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when using multiple libraries, at what point in loading scripts should $.noConflict() be called?

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After including jQuery but before including the conflicting library

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What is an instance where browser sniffing (using $.browser) would be appropriate, instead of feature detection (using $.support)?

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When the attributes passed to a method are different, based on the browser, so there is no way to differentiate using feature detection, such as the following example:

element.add(element, below) for <select> elements
"below" is an object reference for standards compliant browsers, but an integer for IE

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what does this do?
(function($) { /* function body here*/ }) (jQuery);

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It sets $ equal to jQuery, but only in the scope provided.

The purpose is to normalize the $ identifier without affecting the global scope, so that if $.noConflict() has been called, the $ identifier may still be used inside the context of the function.

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which characters are removed by $.trim( string )?

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from the beginning or end of the string only:
\s - space
\n - carriage return
\r - line feed
\f - form feed
\t - tab
\v - vertical tab
\u00A0 - unicode character of some sort

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define $.each(container, callback)

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Iterates items in container and invokes callback for each

container - (Array|Object) to be iterated
callback - (Function) first param is index or key from container, second is the value

returns the container

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how can we break out of iteration while using $.each(container, callback)?

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return false from callback

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define: $.grep(array, callback, invert)

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Filters array, using callback to decide whether each value is added to results

array - (Array)values examined
callback - (Function)function executed, returns true to add, false to skip; passes current value and index
invert - (boolean)flips the callback behavior

returns new array with matched elements

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define: $.map(array, callback)

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Iterates array, invokes callback on each item and returns results

array - (Array)values examined
callback - (Function)return value is added to results, unless null or undefined; passes current value and index

returns new array of callback results

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define: $.inArray(value, array)

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returns index position of first match of value in array

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what is an 'array-like object' in JavaScript?

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Any object that has a length and the concept of indexed arrays

Example: NodeList, returned by document.getElementsByTagName()

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define: $.makeArray( object )

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Converts array-like object to actual JavaScript array

object - an array-like object, such as a NodeList

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define: $.unique(array)

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returns array of unique elements from array

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define: $.merge(array1, array2)

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adds values of array2 into array1

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define $.fx.off

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Enables or disables effects by setting this to true/false

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define: $.extend(deep, target, [src1, src2...])

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simulate extending object, as in inheritance

deep - if true, deep copy is made
target - object to receive new methods
src* - the objects that will be inherited

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(true or false) When using $.extend(deep, target, source1, source2), if an object exists in both source1 and in target, the one in target overrides source1

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false, the method/property in target is overwritten, additionally, if it is declared in source2 that would overwrite source1 in turn

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define: $.param(params, traditional)

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Serializes the passed arguments into URL string

params - (Array|jQuery|Object) can be array of form elements (jQuery wrapped set)
traditional - (bool)forces function to serialize like versions of jQuery before 1.4

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what happens if a jQuery wrapped set that doesn't contain form elements is passed to $.param()?

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the query string shows &undefined=undefined; $.params() does not filter invalid elements

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for $.param(parms), what happens if an element in parms contains an array of key/value pairs? (i.e. how does $.params() handle nested objects?)

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they are passed to the query string like this:

&address[key1]=value1&address[key2]=value2

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define $.isArray(o)

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returns true if o is a JS array, but not any other array-like object (like jQuery wrapped sets)

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define $.isEmptyObject(o)

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returns true if o is JS object with no properties, including ones inherited from prototype

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define $.isFunction(o)

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returns true if o is a JS function.

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browser built-in methods, like alert() and confirm() are returned as functions by $.isFunction(o)

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Except in IE ; (

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define $.isPlainObject(o)

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returns true if o is a JS object created via { } or new Object()

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define $.isXMLDoc(node)

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returns true if node is an XML document, or a node within an XML document

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define $.noop()

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It does nothing; used as a placeholder for optional callbacks in arguments

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define $.contains(haystack, needle)

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determine if DOM element haystack contains DOM element needle

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define $.data(element, name, value)

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stores or retrieves custom data on DOM elments

element - (Element) DOM elm on which data is stored
name - (String) key which value is stored under
value - (Object) if provided, sets name to this

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define $.removeData(element, name)

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removes data with key name stored on a DOM element by the $.data() method

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define $.proxy(function, proxy)

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creates a copy of a function with proxy used as the context (this) when invoked

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define $.proxy(proxy, property)

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Same as $.proxy(function, proxy) except that the function to be modified is inside of proxy already; property defines the element inside proxy that contains the function.

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define $.parseJSON(json)

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parses JSON string provided and returns its evaluation (an object)

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why doesn't $.parseJSON() use the browser JSON.parse() function?

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It does, if it's supported by the browser, otherwise it provides an equivalent trick

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define $.globalEval(code)

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evaluates passed code in global context (JS eval normally executes in the current context)

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how can a script be dynamically included in the page by jQuery?

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$.getScript(url,callback)

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for the context, $.getScript(url,callback), define callback

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callback is a Function executed after the script is loaded ,which receives the text loaded and a status message "success" if it works

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What is special about using $.getScript(...) in older versions of Safari?

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In Safari 2 and younger, the script definitions loaded don't become available in the callback - not until the script block in which it is loaded relinquishes control back to browser.

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what is the difference between a standards compliant box model and IE box model

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in IE's box model, margins are included in the element's size (i.e it measures border to border); in standards compliant browsers, they are not (they measure content edge to content edge)