jQuery on() method examples and advantages

Use jquery on() method to bind Event is an officially recommended method. Next, follow the editor to learn the jquery on() method. Friends, come and join us. Let’s learn

The jQuery on() method is an officially recommended method for binding events.

$(selector).on(event,childSelector,data,function,map)

Several previously common methods expanded from this include.

bind()

　$("p").bind("click",function(){
　　　　alert("The paragraph was clicked.");
　　});
　　$("p").on("click",function(){
　　　　alert("The paragraph was clicked.");
　　});

delegate()

$("#p1").on("click","p",function(){
　　　　$(this).css("background-color","pink");
　　});
　　$("#p2").delegate("p","click",function(){
　　　　$(this).css("background-color","pink");
　　});

live()

　　$("#p1").on("click",function(){
　　　　$(this).css("background-color","pink");
　　});
　　$("#p2").live("click",function(){
　　　　$(this).css("background-color","pink");
　　});

The above three methods are not recommended after jQuery1.8, the official version is As of 1.9, has canceled the use of the live() method, so it is recommended to use the on() method.

tip: If you need to remove the method bound to on(), you can use the off() method.

$(document).ready(function(){
　　$("p").on("click",function(){
　　　　$(this).css("background-color","pink");
　　});
　　$("button").click(function(){
　　　　$("p").off("click");
　　});
});

tip: If your event only requires one operation, you can use the one() method

$(document).ready(function(){
　　$("p").one("click",function(){
　　　　$(this).animate({fontSize:"+=6px"});
　　});
});

trigger() binding

$(selector).trigger(event,eventObj,param1,param2,...)
$(document).ready(function(){
　　$("input").select(function(){
　　　　$("input").after(" Text marked!");
　　});
　　$("button").click(function(){
　　　　$("input").trigger("select");
　　});
});

Multiple events bound to the same function

$(document).ready(function(){
 $("p").on("mouseover mouseout",function(){
  $("p").toggleClass("intro");
 });
});

Multiple events bound to different functions

$(document).ready(function(){
 $("p").on({
  mouseover:function(){$("body").css("background-color","lightgray");}, 
  mouseout:function(){$("body").css("background-color","lightblue");}, 
  click:function(){$("body").css("background-color","yellow");} 
 });
});

Bind custom events

$(document).ready(function(){
 $("p").on("myOwnEvent", function(event, showName){
  $(this).text(showName + "! What a beautiful name!").show();
 });
 $("button").click(function(){
  $("p").trigger("myOwnEvent",["Anja"]);
 });
});

Pass data to function

function handlerName(event) 
{
 alert(event.data.msg);
}
$(document).ready(function(){
 $("p").on("click", {msg: "You just clicked me!"}, handlerName)
});

Applies to uncreated elements

$(document).ready(function(){
 $("p").on("click","p",function(){
  $(this).slideToggle();
 });
 $("button").click(function(){
  $("<p>This is a new paragraph.</p>").insertAfter("button");
 });
});

There are several ways to bind events in jQuery. It is recommended to use the .on() method for binding for two reasons:

1. The on() method can bind events that are dynamically added to page elements

For example, DOM elements that are dynamically added to the page. Events bound with the .on() method do not need to care about the element that registers the event. When it is added, there is no need to bind it again. Some students may be accustomed to using .bind(), .live() or .delegate(). If you look at the source code, you will find that they actually call the .on() method, and the .live() method is in jQuery1. Version 9 has been removed.

bind:
function(
 types, data, fn ) {
  return this.on(
 types, null,
 data, fn );
},
live:
function(
 types, data, fn ) {
  jQuery(
this.context
 ).on( types, this.selector,
 data, fn );
  return this;
},
delegate:
function(
 selector, types, data, fn ) {
  return this.on(
 types, selector, data, fn );
}

Use the .off() method to remove events bound by .on().

2. The on() method can improve the efficiency of event binding

Many articles have mentioned using event bubbling and proxies to improve the efficiency of event binding. Most of them There are no specific differences listed, so to verify, I did a small test.

Assume that 5,000 li's are added to the page, and use chrome developer tool Profiles to test the page loading time.

Normal binding (let’s call it that)

$('li').click(function(){
  console.log(this)
});

Execution time of the binding process

2013 -08-13_190358

Ordinary binding is equivalent to registering click events separately on 5000li. The memory usage is about 4.2M and the binding time is about 72ms.

.on() binding

##

$(document).on('click',
'li',
function(){
  console.log(this)
})

Execution time of the binding process

2013-08-13_191010

.on() binding uses event proxy, only one click event is registered on the document, the memory usage is about 2.2M, and the binding time is about 1ms.

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