jQuery on() method examples and advantages of jquery on() method

jQuery on() method examples and advantages of jquery on() method_jquery

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Release： 2016-05-16 15:42:07

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

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

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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.");
　　});

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delegate()

$("#div1").on("click","p",function(){
　　　　$(this).css("background-color","pink");
　　});
　　$("#div2").delegate("p","click",function(){
　　　　$(this).css("background-color","pink");
　　});

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live()

　　$("#div1").on("click",function(){
　　　　$(this).css("background-color","pink");
　　});
　　$("#div2").live("click",function(){
　　　　$(this).css("background-color","pink");
　　});

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The above three methods are not recommended after jQuery1.8. Officially, in 1.9, has canceled the use of the live() method, so it is recommended All 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");
　　});
});

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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"});
　　});
});

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trigger() binding

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

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Multiple events bound to the same function

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

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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");} 
 });
});

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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"]);
 });
});

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Pass data to function

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

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Applies to uncreated elements

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

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

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

For example, for DOM elements that are dynamically added to the page, events bound with the .on() method do not need to care about when the element that registered the event is added, nor do they need to be bound repeatedly. 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 );
}

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To remove events bound by .on(), use the .off() method.

2. On() method binding events can improve efficiency

Many articles mentioned using event bubbling and proxies to improve the efficiency of event binding, but most of them did not list the specific differences, so to verify, I did a small test.

Assume that 5,000 li's are added to the page, and use Chrome Developer Tools Profiles to test the page loading time.

Normal binding (let’s call it that)

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

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Execution time of 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)
})

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Execution time of binding process

2013-08-13_191010

.on() binding uses an event proxy and only registers a click event on the document. The memory usage is about 2.2M and the binding time is about 1ms.

The above is the entire content of this article. I hope it will be helpful for everyone to learn the jquery on() method.