[js高手之路]打造通用的匀速运动框架

1 function animate(obj, target, speed) { 2 clearInterval(timer); 3 timer = setInterval(function () { 4 if (obj.offsetLeft == target) { 5 clearInterval(timer); 6 } else { 7 obj.style.left = obj.offsetLeft + speed + ‘px‘; 8 } 9 }, 30); 10 }

1 function animate(obj, target, speed) { 2 clearInterval(timer); 3 var cur = 0; 4 timer = setInterval(function () { 5 cur = css( obj, ‘opacity‘) * 100; 6 if( cur == target ){ 7 clearInterval( timer ); 8 }else { 9 cur += speed; 10 obj.style.opacity = cur / 100; 11 obj.style.filter = "alpha(opacity:" + cur + ")"; 12 } 13 }, 30); 14 }

1 function animate(obj, attr, target, speed) { 2 clearInterval(timer); 3 var cur = 0; 4 timer = setInterval(function () { 5 if (attr == ‘opacity‘) { 6 cur = css(obj, ‘opacity‘) * 100; 7 } else { 8 cur = parseInt(css(obj, attr)); 9 } 10 11 if (cur == target) { 12 clearInterval(timer); 13 } else { 14 if (attr == ‘opacity‘) { 15 obj.style.opacity = ( cur + speed ) / 100; 16 obj.style.filter = "alpha(opacity:" + (cur + speed) + ")"; 17 } else { 18 obj.style[attr] = cur + speed + "px"; 19 } 20 } 21 }, 30); 22 }

1 <!doctype html> 2 <html lang="en"> 3 <head> 4 <meta charset="UTF-8"> 5 <title>合并的运动 - by ghostwu</title> 6 <style> 7 img { 8 border: none; 9 opacity: 0.3; 10 filter: alpha(opacity:30); 11 position: absolute; 12 left: 200px; 13 } 14 15 #box { 16 width: 150px; 17 height: 300px; 18 background: red; 19 position: absolute; 20 left: -150px; 21 top: 50px; 22 } 23 24 #box div { 25 width: 28px; 26 height: 100px; 27 position: absolute; 28 right: -28px; 29 top: 100px; 30 background: green; 31 } 32 </style> 33 <script> 34 window.onload = function () { 35 var oImg = document.getElementById("img"), 36 oBox = document.getElementById("box"), 37 timer = null; 38 39 oImg.onmouseover = function () { 40 animate(this, ‘opacity‘, 100, 10); 41 } 42 oImg.onmouseout = function () { 43 animate(this, ‘opacity‘, 30, -10); 44 } 45 46 oBox.onmouseover = function () { 47 animate(this, ‘left‘, 0, 10); 48 } 49 50 oBox.onmouseout = function () { 51 animate(this, ‘left‘, -150, -10); 52 } 53 54 function animate(obj, attr, target, speed) { 55 clearInterval(timer); 56 var cur = 0; 57 timer = setInterval(function () { 58 if (attr == ‘opacity‘) { 59 cur = css(obj, ‘opacity‘) * 100; 60 } else { 61 cur = parseInt(css(obj, attr)); 62 } 63 64 if (cur == target) { 65 clearInterval(timer); 66 } else { 67 if (attr == ‘opacity‘) { 68 obj.style.opacity = ( cur + speed ) / 100; 69 obj.style.filter = "alpha(opacity:" + (cur + speed) + ")"; 70 } else { 71 obj.style[attr] = cur + speed + "px"; 72 } 73 } 74 }, 30); 75 } 76 77 function css(obj, attr) { 78 if (obj.currentStyle) { 79 return obj.currentStyle[attr]; 80 } else { 81 return getComputedStyle(obj, false)[attr]; 82 } 83 } 84 } 85 </script> 86 </head> 87 <body> 88 <div id="box"> 89 <div>分享到</div> 90 </div> 91 <img src="./img/h4.jpg" id="img"/> 92 </body> 93 </html>

 1 <!doctype html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>Document</title>
 6     <style>
 7         img {
 8             border: none;
 9             opacity: 0.3;
10             filter: alpha(opacity:30);
11             position: absolute;
12             left: 200px;
13         }
14 
15         #box {
16             width: 150px;
17             height: 300px;
18             background: red;
19             position: absolute;
20             left: -150px;
21             top: 50px;
22         }
23 
24         #box div {
25             width: 28px;
26             height: 100px;
27             position: absolute;
28             right: -28px;
29             top: 100px;
30             background: green;
31         }
32     </style>
33     <script>
34         window.onload = function () {
35             var oImg = document.getElementById("img"),
36                 oBox = document.getElementById("box");
37 
38             oImg.onmouseover = function () {
39                 animate(this, ‘opacity‘, 100, 10);
40             }
41             oImg.onmouseout = function () {
42                 animate(this, ‘opacity‘, 30, -10);
43             }
44 
45             oBox.onmouseover = function () {
46                 animate(this, ‘left‘, 0, 10);
47             }
48 
49             oBox.onmouseout = function () {
50                 animate(this, ‘left‘, -150, -10);
51             }
52 
53             function animate(obj, attr, target, speed) {
54                 clearInterval(obj.timer);
55                 var cur = 0;
56                 obj.timer = setInterval(function () {
57                     if (attr == ‘opacity‘) {
58                         cur = css(obj, ‘opacity‘) * 100;
59                     } else {
60                         cur = parseInt(css(obj, attr));
61                     }
62 
63                     if (cur == target) {
64                         clearInterval(obj.timer);
65                     } else {
66                         if (attr == ‘opacity‘) {
67                             obj.style.opacity = ( cur + speed ) / 100;
68                             obj.style.filter = "alpha(opacity:" + (cur + speed) + ")";
69                         } else {
70                             obj.style[attr] = cur + speed + "px";
71                         }
72                     }
73                 }, 30);
74             }
75 
76             function css(obj, attr) {
77                 if (obj.currentStyle) {
78                     return obj.currentStyle[attr];
79                 } else {
80                     return getComputedStyle(obj, false)[attr];
81                 }
82             }
83         }
84     </script>
85 </head>
86 <body>
87 <div id="box">
88     <div>分享到</div>
89 </div>
90 <img src="./img/h4.jpg"  id="img"/>
91 </body>
92 </html>

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至此，我们就完成了多物体运动与不同样式的修改

二、让animate函数支持多个样式同时改变

比如：

oBox.onmouseover = function(){
　　animate( this, { "width" : 500, "height" : 400 }, 10 );
}

oBox是一个div元素，animate各参数的意思：

this: 当前div元素

{width : 500, "height" : 400 } : 把宽度变成500, 高度变成400，这两个样式要在同一时间完成，

10: 样式每次在原来的基础上变化10（如width初始值200--> 210, 220, 230.....）

完整的同时运动变化代码：

 1 <!doctype html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>Document</title>
 6     <style>
 7     div {
 8         width: 200px;
 9         height: 200px;
10         background: red;
11     }
12     </style>
13     <script>
14         window.onload = function () {
15             var oBox = document.getElementById("box");
16             oBox.onmouseover = function(){
17 //                animate( this, { "width" : 500, "height" : 500 }, 10 );
18                 animate( this, { "width" : 500, "height" : 400 }, 10 );
19             }
20 
21             function animate(obj, attr, speed) {
22                 clearInterval(obj.timer);
23                 var cur = 0;
24                 obj.timer = setInterval(function () {
25                     for ( var key in attr ) {
26                         if (key == ‘opacity‘) {
27                             cur = css(obj, ‘opacity‘) * 100;
28                         } else {
29                             cur = parseInt(css(obj, key));
30                         }
31                         var target = attr[key];
32                         if (cur == target) {
33                             clearInterval(obj.timer);
34                         } else {
35                             if (key == ‘opacity‘) {
36                                 obj.style.opacity = ( cur + speed ) / 100;
37                                 obj.style.filter = "alpha(opacity:" + (cur + speed) + ")";
38                             } else {
39                                 obj.style[key] = cur + speed + "px";
40                             }
41                         }
42                     }
43                 }, 30);
44             }
45 
46             function css(obj, attr) {
47                 if (obj.currentStyle) {
48                     return obj.currentStyle[attr];
49                 } else {
50                     return getComputedStyle(obj, false)[attr];
51                 }
52             }
53         }
54     </script>
55 </head>
56 <body>
57     <div id="box"></div>
58 </body>
59 </html>

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请自行展开这段代码，这段代码能够同时运动，但是有一个问题：

div的初始宽度与高度（ width : 200, height : 200）

变化步长一样( 10 )

变化时间一样( 每30毫秒变化一次 )

目标( width: 500, height : 400 )

你能想到什么问题吗？( 两个人在同一起跑线上，速度一样，时间一样，但是要同时到达不同的目标，一个500, 一个400 )

答案是很明显的，肯定是目标近的( height : 400 )那个先到达，然后把对象上的定时器关了，另一个目标更远的( width: 500 )肯定到达不了

你可以在这句代码下面，输出当前的值和目标值：

var target = attr[key];

console.log( key, cur, target );

输出来的结果是：

技术分享

从上图可以看出，height已经达到了400px，但是width停在了410px,为什么不是400px ? 因为width = 400的时候，就是( cur == 500 ) 相当于( 400 == 500 ) 不成立，所以执行了else语句，width = cur + 10 = 400 + 10 = 410，然后height到达400px停止了定时器，所以width停在了410px.

那么我们怎么解决这个问题呢？

其实也好办，就是height = 400的时候不要把定时器关了，应该等width = 500的时候再关闭定时器，不就在同一时间，完成了同时到达目标的效果吗？

修改后的代码如下：

 1 <!doctype html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>Document</title>
 6     <style>
 7     div {
 8         width: 200px;
 9         height: 200px;
10         background: red;
11     }
12     </style>
13     <script>
14         window.onload = function () {
15             var oBox = document.getElementById("box");
16             oBox.onmouseover = function(){
17                 animate( this, { "width" : 500, "height" : 400 }, 10 );
18             }
19 
20             function animate(obj, attr, speed) {
21                 clearInterval(obj.timer);
22                 var cur = 0;
23                 obj.timer = setInterval(function () {
24                     var bFlag = true;
25                     for ( var key in attr ) {
26                         if (key == ‘opacity‘) {
27                             cur = css(obj, ‘opacity‘) * 100;
28                         } else {
29                             cur = parseInt(css(obj, key));
30                         }
31                         var target = attr[key];
32                         if (cur != target) {
33                             bFlag = false;
34                             if (key == ‘opacity‘) {
35                                 obj.style.opacity = ( cur + speed ) / 100;
36                                 obj.style.filter = "alpha(opacity:" + (cur + speed) + ")";
37                             } else {
38                                 obj.style[key] = cur + speed + "px";
39                             }
40                         }
41                     }
42                     if ( bFlag ) {
43                         clearInterval( obj.timer );
44                     }
45                 }, 30);
46             }
47 
48             function css(obj, attr) {
49                 if (obj.currentStyle) {
50                     return obj.currentStyle[attr];
51                 } else {
52                     return getComputedStyle(obj, false)[attr];
53                 }
54             }
55         }
56     </script>
57 </head>
58 <body>
59     <div id="box"></div>
60 </body>
61 </html>

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声明一个变量，每次变化完一次( width, height )样式把bFlag = true，只要在for循环中有一个没有到达目标，bFlag的值都是false，这样就不会关闭定时器。当两个都到达目标，才关闭定时器.

三、顺序运动

如样式变化，按顺序来，不是同时变化，如：

oBox.onmouseover = function(){
//回调函数：把函数当做参数传递给另一个函数
　　animate( this, { ‘width‘ : 500 }, 10, function(){
　　　　animate( this, { ‘height‘ : 500 }, 10 );
　　} );
}

当把width变成500px的时候，如果传递了回调函数，再接着执行回调函数里面的运动

修改后的完整代码：

 1 <!DOCTYPE html>
 2 <html>
 3 <head lang="en">
 4     <meta charset="UTF-8">
 5     <title>通用的匀速运动框架 - by ghostwu</title>
 6     <style>
 7         div {
 8             width: 200px;
 9             height: 200px;
10             background: red;
11         }
12     </style>
13     <script>
14         window.onload = function () {
15             var oBox = document.getElementById("box");
16             oBox.onmouseover = function(){
17                 //回调函数： 把函数当做参数传递给另一个函数
18                 animate( this, { ‘width‘ : 500 }, 10, function(){
19                     animate( this, { ‘height‘ : 500 }, 10 );
20                 } );
21             }
22 
23             function animate(obj, attr, speed, fn ) {
24 
25                 clearInterval(obj.timer);
26                 var cur = 0;
27                 obj.timer = setInterval(function () {
28                     var bFlag = true;
29                     for (var key in attr) {
30                         if (key == ‘opacity‘) {
31                             cur = css(obj, ‘opacity‘) * 100;
32                         } else {
33                             cur = parseInt(css(obj, key));
34                         }
35                         var target = attr[key];
36                         if (cur != target) {
37                             bFlag = false;
38                             if (key == ‘opacity‘) {
39                                 obj.style.opacity = ( cur + speed ) / 100;
40                                 obj.style.filter = "alpha(opacity:" + (cur + speed) + ")";
41                             } else {
42                                 obj.style[key] = cur + speed + "px";
43                             }
44                         }
45                     }
46 
47                     if (bFlag) {
48                         clearInterval(obj.timer);
49                         fn && fn.call( obj );
50                     }
51                 }, 30);
52             }
53 
54             function css(obj, attr) {
55                 if (obj.currentStyle) {
56                     return obj.currentStyle[attr];
57                 } else {
58                     return getComputedStyle(obj, false)[attr];
59                 }
60             }
61         }
62     </script>
63 </head>
64 <body>
65 <div id="box"></div>
66 </body>
67 </html>

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