jquery中的animate动态效果是如何通过Js实现的？

你可以看下jquery的源代码，

animate: function( prop, speed, easing, callback ) {
var empty = jQuery.isEmptyObject( prop ),
optall = jQuery.speed( speed, easing, callback ),
doAnimation = function() {
// Operate on a copy of prop so per-property easing won't be lost
var anim = Animation( this, jQuery.extend( {}, prop ), optall );

// Empty animations, or finishing resolves immediately
if ( empty || jQuery._data( this, "finish" ) ) {
anim.stop( true );
}
};
doAnimation.finish = doAnimation;

return empty || optall.queue === false ?
this.each( doAnimation ) :
this.queue( optall.queue, doAnimation );
}

jQuery.speed = function( speed, easing, fn ) {
var opt = speed && typeof speed === "object" ? jQuery.extend( {}, speed ) : {
complete: fn || !fn && easing ||
jQuery.isFunction( speed ) && speed,
duration: speed,
easing: fn && easing || easing && !jQuery.isFunction( easing ) && easing
};

opt.duration = jQuery.fx.off ? 0 : typeof opt.duration === "number" ? opt.duration :
opt.duration in jQuery.fx.speeds ? jQuery.fx.speeds[ opt.duration ] : jQuery.fx.speeds._default;

// normalize opt.queue - true/undefined/null -> "fx"
if ( opt.queue == null || opt.queue === true ) {
opt.queue = "fx";
}

// Queueing
opt.old = opt.complete;

opt.complete = function() {
if ( jQuery.isFunction( opt.old ) ) {
opt.old.call( this );
}

if ( opt.queue ) {
jQuery.dequeue( this, opt.queue );
}
};

return opt;
}