Teach you step by step to write a fade-in and fade-out picture carousel plug-in with annotations (2)_javascript skills

Continuing from the previous article, now comes the second part.
Before we start, let’s talk about the optimization problem mentioned above about writing all functions in a closure. As mentioned before, because we only need to call init during initialization, we can only write init into the closure, and other functional functions can be called as the prototype inheritance method of init. So the previous code can actually be rewritten like this:

Copy the code The code is as follows:

var Hongru= {};
function H$(id){return document.getElementById(id)}
function H$$(c,p){return p.getElementsByTagName(c)}
Hongru.fader = function (){
function init(options){ //options parameters: id (required): picture list parent tag id; auto (optional): automatic running time; index (optional): starting running picture Serial number
var wp = H$(options.id), // Get the parent element of the picture list
ul = H$$('ul',wp)[0], // Get
li = this .li = H$$('li',ul);
this.a = options.auto?options.auto:2; //Automatic running interval
this.index = options.position?options.position :0; //The picture serial number to start running (starting from 0)
this.l = li.length;
this.cur = this.z = 0; //The currently displayed picture serial number&&z-index variable
this.pos(this.index); //Transformation function
}
init.prototype = {
auto:function(){
this.li.a = setInterval(new Function ('Hongru.fader.move(1)'),this.a*1000);
},
move:function(i){//There are two options for parameter i, 1 and -1,1 It means running to the next one, -1 means running to the previous one
var n = this.cur i;
var m = i==1?n==this.l?0:n:nthis.pos(m); //Convert to the previous or next card Zhang
},
pos:function(i){
clearInterval(this.li.a);
this.z;
this.li[i].style.zIndex = this .z; //Increase the z-index of the next picture by one each time
this.cur = i; //Bind the correct serial number of the currently displayed picture
this.auto(); //Automatically run
}
}
return {init:init}
}();

But this is actually problematic. I don’t know if you will find it if it is rewritten like this. , you can no longer call 'Hongru.fader.move()' in the auto function. This is undefined. Then some people will say that since it is the prototype inheritance of init, then call 'Hongru.fader.init.move() )'Isn't that right? In fact, that's not right. I have discussed this issue in my previous article http://www.cnblogs.com/hongru/archive/2010/10/09/1846636.html; init cannot access it before it is instantiated. prototype, so we need to pay attention to two issues when doing this.
One is to use the new keyword to instantiate init during initialization.
The other is that when calling its prototype method inside the code, it must also be called through the object we instantiated. For example, when we initialize the above code, it should be like this

Copy code The code is as follows:

var newFader = new Hongru.fader.init({ //This new is very important
id:'fader'
});

If we want to call the init method in the code, we need to call it through our new instantiation object newFader, such as the auto function above If you want to call the init's move method, just call 'newFader.move()' directly. This will work.
But there is a small problem, that is, the instantiated variable name must be consistent with the name called in the code. So if I change the name of my initialization object, such as using newFader1, then I have to change the source code. This is definitely not possible, so a little trick is to pass one more parameter in init, make the variable name consistent with the parameter when initializing, and then call it through the parameter in the source code. In this way, the problem is successfully solved.
(ps: The reason why new Function is used in the code is also because it can break the scope chain, which is also one of the conditions to ensure that we can structure our code in this way.)
In summary: the previous code should be like this Optimization:

Copy code The code is as follows:

var Hongru={};
function H$(id){return document.getElementById(id)}
function H$$(c,p){return p.getElementsByTagName(c) }
Hongru.fader = function(){
function init(anthor,options){this.anthor=anthor; this.init(options);}
init.prototype = {
init: function(options){ //options parameters: id (required): picture list parent tag id; auto (optional): automatic running time; index (optional): starting picture serial number
var wp = H$(options.id), // Get the parent element of the picture list
ul = H$$('ul',wp)[0], // Get
li = this.li = H$$( 'li',ul);
this.a = options.auto?options.auto:2; //Automatic running interval
this.index = options.position?options.position:0; //Start running The picture serial number (starting from 0)
this.l = li.length;
this.cur = this.z = 0; //The currently displayed picture serial number&&z-index variable
this.pos( this.index); //Transformation function
},
auto:function(){
this.li.a = setInterval(new Function(this.anthor '.move(1)'),this .a*1000);
},
move:function(i){//There are two options for parameter i, 1 and -1, 1 means running to the next one, and -1 means running to the previous one. Zhang
var n = this.cur i;
var m = i==1?n==this.l?0:n:nthis.pos(m); //Convert to the previous or next picture
},
pos:function(i ){
clearInterval(this.li.a);
this.z;
this.li[i].style.zIndex = this.z; //Let the next picture z- each time index plus one
this.cur = i; //Bind the correct serial number of the currently displayed image
this.auto(); //Automatically run
}
}
return {init: init}
}();

It should be initialized like this:

Copy code Code As follows:

var fader = new Hongru.fader.init('fader',{ //Make sure the first parameter is consistent with the variable name
id:'fader'
}) ;

Okay, the code optimization plan ends here. The following is the implementation of the second part of the effect: Fade in and fade out effect
In fact, with the good code structure and logic above, it is relatively easy to add the fade in and fade out effect. The idea is very simple. Make the picture transparent before changing, and then pass Timer to gradually increase transparency. But there are several boundary judgments that are more important. At the same time, when changing transparency in IE and non-IE, you should pay attention to using different css attributes.
The changes to the core code are the following two paragraphs. One is to add the transparency gradient function fade(), and the other is to make the image transparent first in pos() --> and then start executing fade()
Add a code segment in pos():

Copy code The code is as follows:

if(this .li[i].o>=100){ //Set the image transparency to transparent before fading in
this.li[i].o = 0;
this.li[i].style .opacity = 0;
this.li[i].style.filter = 'alpha(opacity=0)';
}
this.li[i].f = setInterval(new Function(this .anthor '.fade(' i ')'),20);

Then add a function fade()

Copy code The code is as follows:

fade:function(i){
if(this.li[i].o>=100){
clearInterval (this.li[i].f); //If the transparency change is completed, clear the timer
if(!this.li.a){ //Make sure all timers are cleared before starting automatic operation. Otherwise, if the controller is clicked too fast, the timer will start the next change before it has time to clear, and the function will be messed up
this.auto();
}
}
else{ //Transparency changes
this.li[i].o =5;
this.li[i].style.opacity = this.li[i].o/100;
this.li[ i].style.filter = 'alpha(opacity=' this.li[i].o ')';
}
}

Okay, it's that simple. But another thing to remember is that you must remember to clear the last timer at the beginning of the pos() call! !
Post the entire source code below:

Copy the code The code is as follows:

var Hongru={};
function H$(id){return document.getElementById(id)}
function H$$(c,p){return p.getElementsByTagName(c) }
Hongru.fader = function(){
function init(anthor,options){this.anthor=anthor; this.init(options);}
init.prototype = {
init: function(options){ //options parameters: id (required): picture list parent tag id; auto (optional): automatic running time; index (optional): starting picture serial number
var wp = H$(options.id), // Get the parent element of the picture list
ul = H$$('ul',wp)[0], // Get
li = this.li = H$$( 'li',ul);
this.a = options.auto?options.auto:2; //Automatic running interval
this.index = options.position?options.position:0; //Start running Picture serial number (starting from 0)
this.l = li.length;
this.cur = this.z = 0; //Currently displayed picture serial number&&z-index variable
/* == Add fade-in and fade-out function ==*/
for(var i=0;ithis.li[i].o = 100; //Set one for each picture Transparency change
this.li[i].style.opacity = this.li[i].o/100; //For non-IE, just use opacity
this.li[i].style.filter = 'alpha(opacity=' this.li[i].o ')'; //IE filter
}
this.pos(this.index); //Transformation function
},
auto:function(){
this.li.a = setInterval(new Function(this.anthor '.move(1)'),this.a*1000);
},
move :function(i){//There are two options for parameter i, 1 and -1, 1 means running to the next picture, -1 means running to the previous picture
var n = this.cur i;
var m = i==1?n==this.l?0:n:nthis.pos(m); //Transform to the previous or next picture
},
pos:function(i){
clearInterval(this.li.a); / /Clear the automatic change timer
clearInterval(this.li[i].f); //Clear the fade effect timer
this.z;
this.li[i].style.zIndex = this.z; //Increase the z-index of the next picture by one each time
this.cur = i; //Bind the correct serial number of the currently displayed picture
this.li.a = false; // Make a mark, which will be used below, indicating that the clear timer has been completed
//this.auto(); //Automatically run
if(this.li[i].o>=100){ // Before the image fades in, set the image transparency to transparent
this.li[i].o = 0;
this.li[i].style.opacity = 0;
this.li[i] .style.filter = 'alpha(opacity=0)';
}
this.li[i].f = setInterval(new Function(this.anthor '.fade(' i ')'),20 );
},
fade:function(i){
if(this.li[i].o>=100){
clearInterval(this.li[i].f); //If the transparency change is completed, clear the timer
if(!this.li.a){ //Make sure all timers are cleared before starting automatic operation. Otherwise, if the controller is clicked too fast, the timer will start the next change before it has time to clear, and the function will be messed up
this.auto();
}
}
else{
this.li[i].o =5;
this.li[i].style.opacity = this.li[i].o/100;
this.li[i].style .filter = 'alpha(opacity=' this.li[i].o ')';
}
}
}
return {init:init}
}();

Everyone should pay attention to the notes I wrote. Some places are more critical.
Let’s take a look at the running effect:

<meta http-equiv="Content-type" content="text/html; charset=utf-8"> <title>step2</title> <style type="text/css"><!-- #fader{position:relative;overflow:hidden;height:300px;width:500px} #fader li{position:absolute;left:0;top:0;} ul,li{list-style:none;margin:0;padding:0} img{display:block;} --></style> <div id="fader"> <ul> <li> <img src="/static/imghwm/default1.png" data-src="http://files.jb51.net/upload/201010/20101011214745247.jpg?x-oss-process=image/resize,p_40" class="lazy" _mce_ alt="Teach you step by step to write a fade-in and fade-out picture carousel plug-in with annotations (2)_javascript skills"> </li> <li> <img src="/static/imghwm/default1.png" data-src="http://files.jb51.net/upload/201010/20101011214745483.jpg?x-oss-process=image/resize,p_40" class="lazy" _mce_ alt="Teach you step by step to write a fade-in and fade-out picture carousel plug-in with annotations (2)_javascript skills"> </li> <li> <img src="/static/imghwm/default1.png" data-src="http://files.jb51.net/upload/201010/20101011214745113.jpg?x-oss-process=image/resize,p_40" class="lazy" _mce_ alt="Teach you step by step to write a fade-in and fade-out picture carousel plug-in with annotations (2)_javascript skills"> </li> <li> <img src="/static/imghwm/default1.png" data-src="http://files.jb51.net/upload/201010/20101011214745525.jpg?x-oss-process=image/resize,p_40" class="lazy" _mce_ alt="Teach you step by step to write a fade-in and fade-out picture carousel plug-in with annotations (2)_javascript skills"> </li> <li> <img src="/static/imghwm/default1.png" data-src="http://files.jb51.net/upload/201010/20101011214745668.jpg?x-oss-process=image/resize,p_40" class="lazy" _mce_ alt="Teach you step by step to write a fade-in and fade-out picture carousel plug-in with annotations (2)_javascript skills"> </li> </ul> </div>
[Ctrl A select all Note:

If you need to introduce external Js, you need to refresh to execute ]
Some people may have noticed that the fade in and fade out here is just a title. In fact, it only has a fade in effect, but it doesn’t matter. The effect is basically the same as a fade out, and even if you want to fade out, you only need to change two sentences. Haha
This part ends here, the next part will add the controller.