JS design mode Note 1, single-case mode

1<script type= "Text/javascript" >2     //single-case mode3     4     //1, each click will generate a new Div5     varcreatemask=function  () {6         returnDocument.body.appendChild (document.createelement (Div));7     }8$ ("button"). Click (function(){9         varmask=Createmask ();Ten mask.show (); One     }); A      -     //2, it's possible that this mask will never be used. -     varMask=document.body.appendchild (Document.createmask ("div")); the$ ("button"). Click (function(){ - mask.show (); -     }); -      +     //3,1) function changes the reference of the variable mask in the body, Createmask is an unsafe function in a multi-person collaborative project. 2) on the other hand, mask this global variable is not necessary.  -     varMask; +     varcreatemask=function(){ A         if(mask) { at             returnMask; -         } -         Else{ -mask=Document.body.appendChild (document.createelement (Div)); -             returnMask; -         } in     }; -     //4, in the form of closures, only a mask is generated to     varcreatemask=function(){ +         varMask; -         return function(){ the             returnmask| | (mask=Document.body.appendChild (document.createelement (div))); *         }; $     }()Panax Notoginseng     //5, final version -     varsingleton=function(FN) { the         varresult; +         return function(){ A             returnresult| | (Result=fn.apply ( This, arguments)); the         } +     } -     varCreatemask=singleton (function(){ $         returnDocument.body.appendChild (document.createelement ("div")); $     }); - A variable is used to hold the return value for the first time, and if it has already been assigned a value, in a subsequent call, the value is returned first, -</script>

JS design mode Note 1, single-case mode