Reusing an AngularJS Directive core code. The idea is to: 1. conceal the actual directive behaviour in a separate JS "class", 2. store that in an Angular Module value, 3. inject that value into an Angular directive, and then 4. just have the directive factory function return the constructed instance of the "class".

directives.js

// Define core directive code + attributes and store that as a module value
angular.module('com.namespace.directives').value('MyDirectiveCore', MyDirectiveCore);

function MyDirectiveCore($compile) {
  this.restrict = 'A';
  this.priority = 10;
  this.link = postLink;

  return this;
  
  function postLink(scope, element, attrs) {
    // Use $compile, scope, element, ... whatever
  }
}

// Define directive to be used in HTML, injecting core definition from previous module
angular.module('com.namespace.directives').directive('myDirective', ['$compile', 'MyDirectiveCore', factory]);

function factory($compile, MyDirectiveCore) {

    return new MyDirectiveCore($compile);
}