jQuery Practical Tips_jquery

The most important thing to use jquery is to be familiar with its properties, methods, etc. The summary below is really good, and the frequently used ones are summarized

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 a jquery object ( Collection object), you 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], $("p").eq(1)[0], $("p").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 an item of jQuery collection
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, while get(n) and index return is a dom element object. For jquery objects, you can only use jquery methods, and for dom objects, you can only use dom methods. For example, you want to get the content of the third

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

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 into the content of the element node with the id of msg, and the page will display bold new content

$("#msg").text(); //Return the text content of the element node with id msg.
$("#msg").text("new content");
//Write "new content" as a normal text string into the content of the element node with id msg, and the page will display new content

$(”#msg”).height(); //Return the height of the element with id msg
$(”#msg”).height(”300″); //Return the id to msg Set the height of the element 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 element click event with id msg
Similarly, blur, focus, select, and submit events can have two calling methods

5. Collection processing function
We do not need to loop through the collection content returned by jquery and process each object separately. jquery has provided us with very convenient methods for processing collections
including. 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]})
//Achieving the effect of interlaced color changing of tables

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

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

7. Support the continuous writing of methods
The so-called continuous writing 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 , operating the style of the element
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 styles in the form of name-value pairs
$(”#msg”).addClass(” select”); //Add a class named select to the element
$(”#msg”).removeClass(”select”); //Remove the class named select for the element
$(”#msg” ).toggleClass("select"); //If it exists (does not exist), delete (add) the class named select

9. Complete event processing function
Jquery has provided us with various With this event processing method, we don't need to write events directly on the html element, but can directly add events to the objects obtained through jquery.
For example:
$("#msg").click(function(){alert("good")}) //Add 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
Among them, 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;i
alert(”Item #” i ”: “ tempArr[ i ]);
}
You 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): Use one or more other objects To extend an object and return the extended object. This is the inheritance method implemented by jquery. For example:
$.extend(settings, options);
//Merge settings and options and merge them. The result is returned to settings, which is equivalent to options inheriting setting and saving the inheritance result in setting.
var settings = $.extend({}, defaults, options);
//Merge defaults and options, and merge them. The result is returned to the setting without overwriting the default content.
can have multiple parameters (combine multiple items and return)
$.map(array, fn): Array mapping (processing conversion). After), save it to another new array, and return the generated new array. For example:
var tempArr=$.map( [0,1,2], function(i){ return i 4; });
tempArr content is: [4,5,6]
var tempArr=$.map( [0,1,2], function(i){ return i > 0 ? i 1 : null; });
tempArr content is: [2,3]
$ .merge(arr1,arr2): Merges two arrays and removes 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 conflicts between custom methods or other class libraries and 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 these contents are put together at the same time, it will cause variable method definition conflicts. , Jquery specifically provides a 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(”p p”).hide();
// Use other libraries $()
$("content").style.display = 'none';