adds strict rule to jshint options (except for test files). "use strict" is added to the main jQuery closure and some "could-be-unsafe" this trickery in effects is silenced.

.jshintrc

@@ -9,6 +9,7 @@
     "node": true,
     "quotmark": "double",
     "smarttabs": true,
+    "strict": true,
     "trailing": true,
     "undef": true,
     "unused": true

src/.jshintrc

@@ -6,8 +6,10 @@
     "evil": true,
     "expr": true,
     "maxerr": 100,
+    "newcap": false,
     "quotmark": "double",
     "smarttabs": true,
+    "strict": true,
     "sub": true,
     "trailing": true,
     "undef": true,

src/effects.js

@@ -233,6 +233,7 @@ jQuery.Animation = jQuery.extend( Animation, {
 });
 
 function defaultPrefilter( elem, props, opts ) {
+	/*jshint validthis:true */
 	var index, prop, value, length, dataShow, tween, hooks, oldfire,
 		anim = this,
 		style = elem.style,

src/intro.js

@@ -12,3 +12,4 @@
  * Date: @DATE
  */
 (function( window, undefined ) {
+"use strict";