JavaScript Design patterns and development practices-7th-Iterator mode

The definition of an iterator pattern: Provides a way to access individual objects in an aggregated object. You can do not care about the internal structure of the object, or you can sequentially access each Harajuku.

Internal iterator: External only requires one initial call

1 vareach =function(ary, callback) {2      for(vari = 0; i < ary.length; i++) {3 Callback.call (Ary[i], I, ary[i]);4     };5 }6 7 //This call was made only once.8Each ([1, 2, 3],function(i, n) {9     //doing an array of operationsTen});

External iterators: Explicit iterations must be made externally

1 //implementation of external iterators, specific customer actions not written here.2 variterator =function(ary) {3     varCurrent = 0;4 5     varNext =function(){6current++;7     };8 9     varIsDone =function(){Ten         returnCurrent >=ary.length; One     }; A  -     varGetCurrent =function(){ -         returnary[current]; the     }; -  -     //since closures are generated here, the returned object method can still be accessed to the ARY -     return { + Next:next, - Isdone:isdone, + getcurrent:getcurrent A     } at}

Abort iterator: Sets the callback function to the callback to return false when it jumps out of the loop

Examples of applications for iterators: When file uploads are available in many ways, avoid using conditional selection statements to choose how to upload

The solution might be:

• Each upload method is written as a function, the function returns the Upload object, and returns False if it is an incompatible upload method.
• Iterate through all the functions of the upload method as an array, until the iteration to an upload method is possible
• Upload using the object returned by this upload method function

JavaScript Design patterns and development practices-7th-Iterator mode