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1. References about page elements
Referencing elements through jquery’s $() includes methods such as id, class, element name, hierarchical relationship of elements, dom or xpath conditions, etc., and the returned object is jquery objects (collection objects) cannot directly call methods defined by dom.

2. Conversion between jQuery objects and dom objects
Only jquery objects can use the methods defined by jquery. Note that there is a difference between dom objects and jquery objects. When calling methods, you should pay attention to whether you are operating on dom objects or jquery objects.
Ordinary dom objects can generally be converted into jquery objects through $().
For example: $(document.getElementById("msg")) is a jquery object, and you can use jquery methods.
Because the jquery object itself is a collection. Therefore, if the jquery object is to be converted into a dom object, one of the items must be retrieved, which can generally be retrieved through an index.
For example: $("#msg")[0], $("div").eq(1)[0], $("div").get()[1], $("td" )[5] These are dom objects, you can use methods in dom, but you can no longer use Jquery methods.
The following writing methods are correct:
$("#msg").html();
$("#msg")[0].innerHTML;
$("# msg").eq(0)[0].innerHTML;
$("#msg").get(0).innerHTML;

3. How to get a certain item in the jQuery collection Item
For the obtained element collection, to obtain an item (specified by index), you can use the eq or get(n) method or the index number. Note that eq returns a jquery object, and get (n) and index return the dom element object. For jquery objects, you can only use jquery methods, and for dom objects, you can only use dom methods. For example, if you want to get the content of the third

element. There are the following two methods:
$("div").eq(2).html(); //Call the jquery object method
$("div").get(2).innerHTML; / /Call dom method attributes

4. The same function implements set and get
This is true for many methods in Jquery, mainly including the following:
$(" #msg").html(); //Return the html content of the element node with id msg.
$("#msg").html("new content");
//Write "new content" as an html string with the id msg In the element node content, the page displays bold new content

$("#msg").text(); //Returns the text content of the element node with the id msg.
$("#msg").text("new content");
//Write "new content" as a normal text string with id msg In the element node content, the page displays new content

$("#msg").height(); //Returns the height of the element with id msg
$(" #msg").height("300"); //Set the height of the element with id msg to 300
$("#msg").width(); //Return the width of the element with id msg
$("#msg").width("300"); //Set the width of the element with id msg to 300

$("input").val("); / /Return the value of the form input box
$("input").val("test"); //Set the value of the form input box to test

$("#msg") .click(); //Trigger the click event of the element with id msg
$("#msg").click(fn); //Add a function for the click event of the element with id msg
Similarly blur, focus, select, and submit events can all have two calling methods

5. Collection processing function
For the collection content returned by jquery, we do not need to loop through it ourselves and process each The objects are processed separately, and jquery has provided us with a very convenient method for processing collections.
includes two forms:
$("p").each(function(i){this.style.color. =['#f00','#0f0','#00f'][ i ]})
//Set different font colors for the p elements with indexes 0, 1, and 2 respectively.

$("tr").each(function(i){this.style.backgroundColor=['#ccc','#fff'][i%2]})
//Achieve alternate rows in the table Color changing effect

$("p").click(function(){alert($(this).html())})
//Added click event for each p element, Click on a p element and its content will pop up

6. Extend the functions we need
$.extend({
min: function(a, b){return a max: function(a, b){return a > b?a:b; }
}); //Extended min and max methods for jquery
Use the extended method (called via "$.method name"):
alert("a=10,b=20,max=" $.max(10,20) ",min=" $. min(10,20));

7. Support method concatenation
The so-called concatenation means that you can continuously call various methods on a jquery object.
For example:
$("p").click(function(){alert($(this).html())})
.mouseover(function(){alert('mouse over event ')})
.each(function(i){this.style.color=['#f00','#0f0','#00f'][ i ]});

8. Manipulating the style of elements
mainly includes the following methods:
$("#msg").css("background"); //Return the background color of the element
$ ("#msg").css("background","#ccc") //Set the background of the element to gray
$("#msg").height(300); $("#msg"). width("200"); //Set width and height
$("#msg").css({ color: "red", background: "blue" });//Set in the form of name-value pairs Define the style
$("#msg").addClass("select"); //Add a class named select to the element
$("#msg").removeClass("select"); // Delete the class with the element name select
$("#msg").toggleClass("select"); //If it exists (does not exist), delete (add) the class with the name select



9. Complete event processing function

Jquery has provided us with various event processing methods. We do not need to write events directly on html elements, but can directly Add events to objects obtained through jquery.
For example:
$("#msg").click(function(){alert("good")}) //Added a click event to the element
$("p").click (function(i){this.style.color=['#f00','#0f0','#00f'][ i ]})
//Set three different p element click events respectively Different handling
Several custom events in jQuery:
(1) hover(fn1, fn2): A method that imitates hover events (mouse moves over an object and out of the object). When the mouse moves over a matching element, the first specified function will be triggered. When the mouse moves out of this element, the specified second function will be triggered.
//When the mouse is placed on a row of the table, set the class to over and set it to out when leaving.
$("tr").hover(function(){
$(this).addClass("over");
},
function(){
$(this) .addClass("out");
});
(2) ready(fn): Bind a function to be executed when the DOM is loaded and ready for query and manipulation.
$(document).ready(function(){alert("Load Success")})
//When the page is loaded, it prompts "Load Success", which is equivalent to the onload event. Equivalent to $(fn)
(3) toggle(evenFn,oddFn): Switch the function to be called every time it is clicked. If a matching element is clicked, the first function specified is triggered, and when the same element is clicked again, the second function specified is triggered. Each subsequent click repeats the call to these two functions in turn.
//Rotate adding and deleting the class named selected every time you click.
$("p").toggle(function(){
$(this).addClass("selected");
},function(){
$(this).removeClass( "selected");
});
(4) trigger(eventtype): Trigger a certain type of event on each matching element.
For example:
$("p").trigger("click"); //Trigger the click event of all p elements
(5) bind(eventtype,fn), unbind(eventtype): event Binding and unbinding
removes (adds) the bound event from each matching element.
For example:
$("p").bind("click", function(){alert($(this).text());}); //Add click for each p element Event
$("p").unbind(); //Delete all events on all p elements
$("p").unbind("click") //Delete all single events on all p elements Click event

10. Several practical special effects functions
The toggle() and slidetoggle() methods provide state switching functions.
For example, the toggle() method includes hide() and show() methods.
The slideToggle() method includes the slideDown() and slideUp methods.

11. Several useful jQuery methods
$.browser. Browser type: Detect browser type. Valid parameters: safari, opera, msie, mozilla. For example, if you check whether it is IE: $.browser.isie, if it is an IE browser, it will return true.
$.each(obj, fn): General iteration function. Can be used to iterate over objects and arrays approximately (instead of looping).
For example,
$.each( [0,1,2], function(i, n){ alert( "Item #" i ": " n ); });
is equivalent to:
var tempArr=[0,1,2];
for(var i=0;ialert("Item #" i ": " tempArr[ i ]) ;
}
can also process json data, such as
$.each( { name: "John", lang: "JS" }, function(i, n){ alert( "Name: " i ", Value: " n ); });
The result is:
Name:name, Value:John
Name:lang, Value:JS
$.extend(target,prop1,propN) : Extend an object with one or more other objects and return the extended object. This is the inheritance method implemented by jquery.
For example:
$.extend(settings, options);
//Merge settings and options, and return the merged result to settings, which is equivalent to options inheriting setting and saving the inherited result in setting.
var settings = $.extend({}, defaults, options);
//Merge defaults and options, and return the merged result to the setting without overwriting the default content.
Can have multiple parameters (combine multiple parameters and return)
$.map(array, fn): array mapping. Saves the items in an array (after processing the transformation) into a new array and returns the resulting new array.
For example:
var tempArr=$.map( [0,1,2], function(i){ return i 4; });
The content of tempArr is: [4,5,6]
var tempArr=$.map( [0,1,2], function(i){ return i > 0 ? i 1 : null; });
The content of tempArr is: [2,3]
$.merge(arr1,arr2): Merge two arrays and delete duplicate items.
For example: $.merge( [0,1,2], [2,3,4] ) //Return [0,1,2,3,4]
$.trim(str): Delete Whitespace characters at both ends of the string.
For example: $.trim(" hello, how are you? "); //Return "hello, how are you? "

12. Solve the problem with custom methods or other class libraries Conflicts with jQuery
Many times we define the $(id) method ourselves to get an element, or some other js libraries such as prototype also define the $method. If we put these contents together at the same time, Will cause variable method definition conflict, Jquery provides a special method to solve this problem.
Use the jQuery.noConflict(); method in jquery to transfer control of the variable $ to the first library that implements it or the previously customized $ method. When using Jquery later, just replace all $ with jQuery. For example, the original reference object method $("#msg") is changed to jQuery("#msg").
For example:
jQuery.noConflict();
// Start using jQuery
jQuery("div p").hide();
// Use $() from other libraries
$("content").style.display = 'none';