AngularJs(Part 8)--Filters

Filters
AngularJS provides fileters to transfrom data from one kind to another . For example:
    {{user.birthday | date:'yyyy-MM-dd'}}
In this example, the date filter is used to format user's birthday.
A filter is nothing more than a global,named function that is invoked in view using the pipe(|)
symbol with parameters separated by the colon(:).
Fileters can be combined(chained) to form a pipeline.
    {{myLongString | limiTo:80 | lowercase}}
    
Generally,there are two kind of filters built in AngujarJS: formatting fileters and array-transforming
filters.
    array-transforming filters:limitTo; filter;orderBy.
    ng-repeat="item in logs | filter:{name:criteria,done:false}"
    the "filter" filter can also accept a function as it parameter.
    ng-repeat="item in logs | filter:checkName"
    
    $scope.checkName=function(item){
        return item.done=true;
    }

sometime, we want the result of the "filter" filter for other use, like showing the size, then we can
    ng-repeat="item in filteredLogs=(logs | filter:checkName)"
    
    Total:{{filteredLogs.length}}