$element
is one of four locals that $compileProvider
gives to $controllerProvider
which then gets given to $injector
. The injector injects locals in your controller function only if asked.
The four locals are:
$scope
$element
$attrs
$transclude
The official documentation: AngularJS $compile Service API Reference - controller
The source code from Github angular.js/compile.js:
function setupControllers($element, attrs, transcludeFn, controllerDirectives, isolateScope, scope) {
var elementControllers = createMap();
for (var controllerKey in controllerDirectives) {
var directive = controllerDirectives[controllerKey];
var locals = {
$scope: directive === newIsolateScopeDirective || directive.$$isolateScope ? isolateScope : scope,
$element: $element,
$attrs: attrs,
$transclude: transcludeFn
};
var controller = directive.controller;
if (controller == '@') {
controller = attrs[directive.name];
}
var controllerInstance = $controller(controller, locals, true, directive.controllerAs);