javascript - What is Angularjs $compile function 2nd and 3rd parameter -

i have example

<div ng-controller="myctrl">     <div compile-template ng-bind-html="post"></div> </div> 

and angularjs code:

angular.module('myapp',[])  .controller('myctrl', function($scope, $sce,$timeout) {     $scope.name = 'world';     $scope.post = $sce.trustashtml("<h1>hello {{name}}</h1>");     $timeout(function(){      $scope.name = "3333";     },3000); });  angular.module("myapp").directive('compiletemplate', ["$compile", "$parse", function($compile, $parse) {     return {         restrict: 'a',         link: function($scope, element, attr) {             var parse = $parse(attr.ngbindhtml);             function value() { return (parse($scope) || '').tostring(); }              $scope.$watch(value, function() {                 $compile(element, null,-9999)($scope);              });         }     } }]);       

if carefully, notice function.

$compile(element, null,-9999)($scope); 

if make $compile(element)($scope), not work longer.

why that?

here fiddle.

http://jsfiddle.net/bugd67e3/4/

the third argument of $compile maxpriority. the docs:

only apply directives lower given priority (only effects root element(s), not children)

when run $compile(element, null,-9999)($scope);, telling compiler skip directives on element priority greater -9999. why compiletemplate directive not "self-compiled" because default priority 0 , ngbindhtml not run twice, since:

this directive executes @ priority level 0.

when removing third param ngbindhtml compiled , linked again. same thing happen compiletemplate directive well. since have set $watchand $compile called inside of it,

[$rootscope:infdig] 10 $digest() iterations reached. aborting!

error because of infinite "self-compilation". 1 of called "double compilation" issues.

the second argument transclude function (it not play role in case since passed null):

function available directives - deprecated.