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A brief analysis of JS sports_javascript skills

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May 16, 2016 pm 03:23 PM

jssports

Principle of object motion: Movement changes occur by changing the position of an object. Any movement is relative, just like the movement formula in physics: s (to be achieved) = s0 (current style value) + vt.

Method:
1. Use absolute positioning for moving objects
2. Move the object by changing the attributes (left, right, top, bottom) of the positioned object. For example, to move to the right or left, you can use offsetLeft(offsetRight) to control the left and right movement.
Steps:
1. Before starting movement, clear the existing timer (because: if you click the button continuously, the object will move faster and faster, causing movement chaos)
2. Turn on the timer and calculate the speed
3. Separate movement and stop (if/else), determine the stop condition, and execute movement

Key points:

1. Multiple objects

Attach the timer to the object
2. Chain motion

Call the timer in a loop: start another timer in the fnEnd function
3. Multi-valued sports

Loop attribute value array: a timer time, execute multiple attribute value changes
Determine that the movement is over and all attributes have reached the predetermined values: add a Boolean flag, at the beginning, var bStop=true; //Assumption: all values have arrived; judge during the loop, if if(cur!=json[ attr]) bStop=false;

1. Timer
In javascript, there are two dedicated functions for timers, they are:
1. Countdown timer: timename=setTimeout("function();",delaytime);
2. Loop timer: timename=setInterval("function();",delaytime);
Function() is an event function to be executed when the timer is triggered. It can be one function, several functions, or a JavaScript statement. It only needs to be separated by "; delaytime" is the time of the interval, in milliseconds.
A countdown timer triggers an event after a specified time, while a loop timer triggers an event repeatedly when the interval arrives. The difference is that the former only works once, while the latter works continuously.
The countdown timer is generally used in situations where the page only needs to be triggered once. For example, after clicking a certain button, the page will jump to the corresponding site after a certain period of time. It can also be used to determine whether a visitor is an "old visitor" on your site. "Customer", if not, you can jump to the corresponding site after 5 seconds or 10 seconds, and then tell him that he can press a certain button somewhere to quickly enter when he comes back later.
Loop timers are generally used for effects that need to be executed repeatedly on the site, such as a JavaScript scroll bar or status bar. They can also be used to represent the background of the page with a picture of flying snow. These events need to be run at intervals.
Sometimes we also want to remove some added timers. In this case, we can use clearTimeout(timename) to turn off the countdown timer, and use clearInterval(timename) to turn off the loop timer.

2. Exercise research
1. Movement: uniform motion (making objects move)
Using timers
Add absolute positioning to DIV
offsetLeft

Problem: Stop character is reached at a certain position
Solution: Make a judgment and turn off the timer when the conditions are met (save the timer)
The speed becomes slower (usually the time is not changed, but the number-speed is changed)
Use variables to store speed

Problem: When taking 7 and offsetLeft is not equal to 300, the div cannot stop
Solution:>=300 //Stop at 301

Problem: Clicking the button after reaching 300 still keeps going
Reason: Click the button, execute the function, and start the timer (execute the current function at least once)
Solution: Add else (execute before reaching the target)

Problem: Click continuously, the speed becomes faster
Reason: Each time you click, a timer will start. After several clicks, several timers will work at the same time
Solution: To ensure that only one timer works at a time, first cearlnterval ()

Example 1, share to:

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>分享到</title>
<style>
#div1 {width:150px; height:200px; background:green; position:absolute; left:-150px;}
#div1 span {position:absolute; width:20px; height:60px; line-height:20px; background:blue; right:-20px; top:70px;}
</style>
<script>
window.onload=function ()
{
  var oDiv=document.getElementById('div1');
  
  oDiv.onmouseover=function ()
  {
    startMove(0);
  };
  oDiv.onmouseout=function ()
  {
    startMove(-150);
  };
};

var timer=null;

function startMove(iTarget)
{
  var oDiv=document.getElementById('div1');
  
  clearInterval(timer);
  timer=setInterval(function (){
    var speed=0;
    
    if(oDiv.offsetLeft>iTarget)
    {
      speed=-10;
    }
    else
    {
      speed=10;
    }
    
    if(oDiv.offsetLeft==iTarget)
    {
      clearInterval(timer);
    }
    else
    {
      oDiv.style.left=oDiv.offsetLeft+speed+'px';
    }
  }, 30);
}
</script>
</head>

<body>
<div id="div1">
  <span>分享到</span>
</div>
</body>
</html>

The effect is as follows:

Example 2, fade in and out:

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>淡入淡出</title>
<style>
#div1 {width:200px; height:200px; background:red; filter:alpha(opacity:30); opacity:0.3;}
</style>
<script>
window.onload=function ()
{
  var oDiv=document.getElementById('div1');
  
  oDiv.onmouseover=function ()
  {
    startMove(100);
  };
  oDiv.onmouseout=function ()
  {
    startMove(30);
  };
};

var alpha=30;
var timer=null;

function startMove(iTarget)
{
  var oDiv=document.getElementById('div1');
  
  clearInterval(timer);
  timer=setInterval(function (){
    var speed=0;
    
    if(alpha<iTarget)
    {
      speed=10;
    }
    else
    {
      speed=-10;
    }
    
    if(alpha==iTarget)
    {
      clearInterval(timer);
    }
    else
    {
      alpha+=speed;
      
      oDiv.style.filter='alpha(opacity:'+alpha+')';
      oDiv.style.opacity=alpha/100;
    }
  }, 30);
}
</script>
</head>

<body>
<div id="div1"></div>
</body>
</html>

The effect is as follows:

Stop conditions for uniform motion
Close enough

Example 3, stopping conditions for uniform motion:

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>匀速运动的停止条件</title>
<style>
#div1 {width:100px; height:100px; background:red; position:absolute; left:600px; top:50px;}
#div2 {width:1px; height:300px; position:absolute; left:300px; top:0; background:black;}
#div3 {width:1px; height:300px; position:absolute; left:100px; top:0; background:black;}
</style>
<script>
var timer=null;

function startMove(iTarget)
{
  var oDiv=document.getElementById('div1');
  
  clearInterval(timer);
  timer=setInterval(function (){
    var speed=0;
    
    if(oDiv.offsetLeft<iTarget)
    {
      speed=7;
    }
    else
    {
      speed=-7;
    }
    
    if(Math.abs(iTarget-oDiv.offsetLeft)<=7)
    {
      clearInterval(timer);
      
      oDiv.style.left=iTarget+'px';
    }
    else
    {
      oDiv.style.left=oDiv.offsetLeft+speed+'px';
    }
  }, 30);
}
</script>
</head>

<body>
<input type="button" value="到100" onclick="startMove(100)" />
<input type="button" value="到300" onclick="startMove(300)" />
<div id="div1"></div>
<div id="div2"></div>
<div id="div3"></div>
</body>
</html>

2.变速运动（缓冲运动）
逐渐变慢,最后停止
距离越远速度越大
    速度有距离决定
    速度=(目标值-当前值)/缩放系数
    如果没有缩放系数t速度太大,瞬间到达终点.没有过程

问题：并没有真正到达300
原因：速度只剩0.9 //像素是屏幕能够显示的最/J库位，并不会四舍五入掉
Math.ceil ()向上取整
Math.floor ()向下取整

问题：向左走，又差一块--Math.floor ()
判断：三目 speed=speed>0 ? Math.ceil ( speed ): Math.floor ( speed )

示例,缓冲运动：

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>缓冲运动</title>
<style>
#div1 {width:100px; height:100px; background:red; position:absolute; left:600px; top:50px;}
#div2 {width:1px; height:300px; position:absolute; left:300px; top:0; background:black;}
</style>
<script>
function startMove()
{
  var oDiv=document.getElementById('div1');
  setInterval(function (){
    var speed=(300-oDiv.offsetLeft)/10;
    speed=speed>0&#63;Math.ceil(speed):Math.floor(speed);
    
    oDiv.style.left=oDiv.offsetLeft+speed+'px';
    
    document.title=oDiv.offsetLeft+','+speed;
  }, 30);
}
</script>
</head>

<body>
<input type="button" value="开始运动" onclick="startMove()" />
<div id="div1"></div>
<div id="div2"></div>
</body>
</html>

效果如下：

3.多物体运动
多个div ,鼠标移入变宽
运动框架传参obj,知道让哪个物体动起来
用到缓冲一定要取整

问题：div没运动回去 //清除前一个定时器
原因：只有一个定时器
解决：加物体上的定时器，使每个物体都有一个定时器。定时器作为物体属性

多个div淡入淡出
首先关闭物体上的定时器
经验：多物体运动框架所有东西都不能共用

问题：不是因为定时器,而是因为alpha
解决：作为属性附加到物体上 /不以变量形式存在

offset 的 bug

加border变宽

offsetWith并不是真正的width ,它获取的是盒模型尺寸
解决：躲着宽度扔到行间,parselnt ( oDiv.style.width )

进一步解决： getStyle ( obj, name ) currentStyle , getComputedStyle
加border ,只要offset就有问题去掉offset

示例,多物体运动：

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
div {width:100px; height:50px; background:red; margin:10px; border:10px solid black;}
</style>
<script>
window.onload=function ()
{
  var aDiv=document.getElementsByTagName('div');
  
  for(var i=0;i<aDiv.length;i++)
  {
    aDiv[i].timer=null;
    
    aDiv[i].onmouseover=function ()
    {
      startMove(this, 400);
    };
    
    aDiv[i].onmouseout=function ()
    {
      startMove(this, 100);
    };
  }
};

function startMove(obj, iTarget)
{
  clearInterval(obj.timer);
  obj.timer=setInterval(function (){
    var speed=(iTarget-obj.offsetWidth)/6;
    speed=speed>0&#63;Math.ceil(speed):Math.floor(speed);
    
    if(obj.offsetWidth==iTarget)
    {
      clearInterval(obj.timer);
    }
    else
    {
      obj.style.width=obj.offsetWidth+speed+'px';
    }
  }, 30);
}
</script>
</head>

<body>
<div></div>
<div></div>
<div></div>
</body>
</html>

效果如下：

4.任意值运动
任意值运动的单位分为透明度和px。

px单位的任意值

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
div {width:200px; height:200px; margin:20px; float:left; background:yellow; border:10px solid black; font-size:14px;}
</style>
<script>
window.onload=function ()
{
  var oDiv1=document.getElementById('div1');
  oDiv1.onmouseover=function (){startMove(this, 'height', 400);};
  oDiv1.onmouseout=function (){startMove(this, 'height', 200);};
  
  var oDiv2=document.getElementById('div2');
  
  oDiv2.onmouseover=function (){startMove(this, 'width', 400);};
  oDiv2.onmouseout=function (){startMove(this, 'width', 200);};
  
  var oDiv3=document.getElementById('div3');
  oDiv3.onmouseover=function (){startMove(this, 'fontSize', 50);};
  oDiv3.onmouseout=function (){startMove(this, 'fontSize', 14);};
  
  var oDiv4=document.getElementById('div4');
  oDiv4.onmouseover=function (){startMove(this, 'borderWidth', 100);};
  oDiv4.onmouseout=function (){startMove(this, 'borderWidth', 10);};
};

function getStyle(obj, name)
{
  if(obj.currentStyle){return obj.currentStyle[name];}
  else{return getComputedStyle(obj, false)[name];}
}

function startMove(obj, attr, iTarget)
{
  clearInterval(obj.timer);
  obj.timer=setInterval(function (){
    var cur=parseInt(getStyle(obj, attr));
    
    var speed=(iTarget-cur)/6;
    speed=speed>0&#63;Math.ceil(speed):Math.floor(speed);
    
    if(cur==iTarget)
    {
      clearInterval(obj.timer);
    }
    else
    {
      obj.style[attr]=cur+speed+'px';
    }
  }, 30);
}
</script>
</head>

<body>
<div id="div1">变高</div>
<div id="div2">变宽</div>
<div id="div3">safasfasd</div>
<div id="div4"></div>
</body>
</html>

效果如下：

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
div {width:200px; height:200px; margin:20px; float:left; background:yellow; border:10px solid black; font-size:14px;}
</style>
<script>
window.onload=function ()
{
var oDiv1=document.getElementById('div1');
oDiv1.onmouseover=function (){startMove(this, 'height', 400);};
oDiv1.onmouseout=function (){startMove(this, 'height', 200);};

var oDiv2=document.getElementById('div2');

oDiv2.onmouseover=function (){startMove(this, 'width', 400);};
oDiv2.onmouseout=function (){startMove(this, 'width', 200);};

var oDiv3=document.getElementById('div3');
oDiv3.onmouseover=function (){startMove(this, 'fontSize', 50);};
oDiv3.onmouseout=function (){startMove(this, 'fontSize', 14);};

var oDiv4=document.getElementById('div4');
oDiv4.onmouseover=function (){startMove(this, 'borderWidth', 100);};
oDiv4.onmouseout=function (){startMove(this, 'borderWidth', 10);};
};

function getStyle(obj, name)
{
if(obj.currentStyle){return obj.currentStyle[name];}
else{return getComputedStyle(obj, false)[name];}
}

function startMove(obj, attr, iTarget)
{
clearInterval(obj.timer);
obj.timer=setInterval(function (){
var cur=parseInt(getStyle(obj, attr));

var speed=(iTarget-cur)/6;
speed=speed>0&#63;Math.ceil(speed):Math.floor(speed);

if(cur==iTarget)
{
clearInterval(obj.timer);
}
else
{
obj.style[attr]=cur+speed+'px';
}
}, 30);
}
</script>
</head>

<body>
<div id="div1">变高</div>
<div id="div2">变宽</div>
<div id="div3">safasfasd</div>
<div id="div4"></div>
</body>
</html>

效果如下：

透明度的任意值，需要做判断：

判断
var cur=0
if ( attr== 'opacity '){
cur=parseFloat ( getStyle ( obj, attr)) *100
}else{

}
设置样式判断
if ( attr== 'opacity '){
obj.style.fiIter = 'alpha ( opacity: '( cur+speed ) + ')'
obj.style.opacity= ( cur+speed ) /100
}else{

}

5.链式运动
多出来的一个参数，只有传进去的时候才调用
鼠标移入变宽，结束之后弹出abc
先横向展开.再以向展开
鼠标移出,先变回不透明，变矮，变窄

三.封装运动框架

基于以上的分析与总结，封装运动框架move.js如下：

function getStyle(obj, name)
{
  if(obj.currentStyle)
  {
    return obj.currentStyle[name];
  }
  else
  {
    return getComputedStyle(obj, false)[name];
  }
}

function startMove(obj, json, fnEnd)
{
  clearInterval(obj.timer);
  obj.timer=setInterval(function (){
    var bStop=true;    //假设：所有值都已经到了
    
    for(var attr in json)
    {
      var cur=0;
      
      if(attr=='opacity')
      {
        cur=Math.round(parseFloat(getStyle(obj, attr))*100);
      }
      else
      {
        cur=parseInt(getStyle(obj, attr));
      }
      
      var speed=(json[attr]-cur)/6;
      speed=speed>0&#63;Math.ceil(speed):Math.floor(speed);
      
      if(cur!=json[attr])
        bStop=false;
      
      if(attr=='opacity')
      {
        obj.style.filter='alpha(opacity:'+(cur+speed)+')';
        obj.style.opacity=(cur+speed)/100;
      }
      else
      {
        obj.style[attr]=cur+speed+'px';
      }
    }
    
    if(bStop)
    {
      clearInterval(obj.timer);
            
      if(fnEnd)fnEnd();
    }
  }, 30);
}

move.js运动框架基本满足现在网页上所有动画的需求（不包括css3）。

以上就是本文的全部内容，希望对大家的学习有所帮助。

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