怎样用JavaScript制作淡入淡出的文字效果

1、用jquery的话，fadeIn ，fadeOut , fadeToggle
2、配合css3,用animation或transform变化 opacity 在 0~1间变换就行
3、用setTimeout或requestAnimationFrame 变换 opacity

给你一个之前写的淡入淡出的函数

var $fade={
     id:function(id){return document.getElementById(id)},
     set:function(o,v){o.filters ? o.style.filter='alpha(opacity='+v+')':o.style.opacity=v/100},
     in:function(elem, speed, opacity){
          speed = speed || 20;
          opacity = opacity || 100;
          elem.style.display = 'block';
          $fade.set(elem, 0);
          var val=0;
          (function(){
               $fade.set(elem, val);
               val += 5;
               if(val<=opacity){setTimeout(arguments.callee, speed)}
          })();
     },
     out:function(elem, speed, opacity){
          speed = speed || 20;
          opacity = opacity || 0;
          var val = 100;
          (function(){
               $fade.set(elem, val);
               val-=5;
               if(val>=opacity){
                  setTimeout(arguments.callee, speed)
               }else if(val<0){
                  elem.style.display='none'
               }
          })();
     }
}
var obj=$fade.id('output');
$fade.out(obj);

$fade.in()是淡入，$fade.out()是淡出，把目标元素当做参数传过去

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