1.
markers on a DOM element (attribute, element name,
comment or CSS class);
"... a way to tech HTML new tricks.";
anything (within your app) ;
a function that's attached to a DOM element:
a whole execution environment;
a micro-application;
<!-- Built in directive -->
<div ng-repeat="item in items"> </div>
<!-- Custom directive -->
<my-directive> </my-directive>
<!-- OR -->
<div my-directive> </div>

2.
event handling;
behavior management;
template pre-processing and insertion;
data-binding;
UI Widgets;
much more.

3.
1. Declarative, Model-Driven Behaviour
2. Modularity, Reusability across contexts
3. Keep it local
<!-- Imperative Way -->
<button id="1" class="B C"></button>
<!-- V.s. Declarative way-->
<button my-action-handler></button>

4.
Directive Names Angular uses a convention borrowed
from other JS projects: names in HTML are hyphenated
<my-directive> </my-directive>
.directive('myDirective', function(){
});
while identifiers in the JS are camel-cased

5.
angular
.module('myApp', [])
.directive('myDirective', function(){
return{
link: function(scope, lement, attrs, ctrl){
element.bind("mouseenter", function(){
element.css({color: 'red'});
});
},
require: '',
controller: ['$scope', '$element', function($scope, $element){}],
scope: false,
transclude: false,
restrict: 'E',
template: "<div>Hello, World!</div>"
};
});
Everything but is optional.

6.
The params are supplied as args not injected:
scope associated with the directive
DOM element wrapped by jQLite
an object containing the html attributes defined
on the element
Reference to controller object

7.
Templates can be stored as strings on the
property;
They can also be loaded from a file, using
property

8.
Directives can be restricted to a specific context, so
the accidentally usage can be avoided:
- Element
- Attribute
- Class
Can be used as a single string: ' ';
Defaults to ' '

9.
We have the option, in directives, of using either:
the same scope (scope from the environment that
directive lives)
a child scope that inherits from current scope
a new isolate scope
.directive('myDirective', function(){
return {
//scope: false // default, use local scope
//scope: true // create a child of local scope
//Create a new isolate scope
scope: {
}
}
});

10.
Angular provides ways to bind the value of properties in
isolate scope to attributes on the element, using special
operators:
- Local scope property
- Bi-directional binding
- Parent execution binding
scope: {
local1: '@attr1',
local2: '=attr1',
local3: '&attr3'
}

11.
Plunker link

12.
Transclude allow to pass in an entire template,
including its scope, to a directive.
In order for scope to be passed in, the scope option
must be isolated, , or set to .
<div sidebox title="Links">
<ul>
<li>First link</li>
<li>Second link</li>
</ul>
</div>
<script type="text/ng-template" id="directive.template.html">
{{ title }}
angular.module('myApp', [])
.directive('sidebox', function() {
return {
restrict: 'EA',
scope: {
title: '@'
},
transclude: true,
templateUrl: 'directive.template.html'
});

13.
The main use case for a controller is when we want to provide reusable
behavior between directives
As the link function is only available inside the current directive, any
behavior defined within is not shareable
Because a directive can require the controller of another directive,
controllers are a good choice for placing actions that will be used by
multiple directives.

14.
The option can be set to a string or an array of
strings.
The string(s) contain the name of another directive.
is used to provide the controller of the required
directive as the fourth parameter of the current directive’s
linking function
The string(s) provided to the require option may optionally be prefixed with the
following options:
- If the required controller is not found on the directive provided, pass
look upwards on its parent chain for the controller in the require option
optionally require the controller and look up the parent chain for the
controller

15.
<level-one>
<level-two>
<level-three>
Hello {{name}}
</level-three>
</level-two>
</level-one>
function createDirective(name){
return function(){
return {
restrict: 'E',
compile: function(tElem, tAttrs){
console.log(name + ': compile => ' + tElem.html());
return {
pre: function(scope, iElem, iAttrs){
console.log(name + ': pre link => ' + iElem.html());
},
post: function(scope, iElem, iAttrs){
console.log(name + ': post link => ' + iElem.html());
}
}
}
}
}
}
angular.module('myModule', [])
.directive('levelOne', createDirective('levelOne'))
.directive('levelTwo', createDirective('levelTwo'))
.directive('levelThree', createDirective('levelThree'));
let AngularJS process three nested directives where each directive has its own
, and function that logs a line to the console so we can identify them.

16.
1. Angular start to process the DOM when it detects that the DOM is ready;
2. it bumps into the element and knows from its directive definition that
some action needs to be performed:
1. Because a function is defined in the directive definition
object, it is called and the element's DOM is passed as an argument to the
function;
2. Once the compile function of the directive has run, Angular
recursively traverses deeper into the DOM and repeats the same compilation
step for the and <level-three> elements.

17.
1. After Angular travels down the DOM and has run all the
functions, it traverses back up again and runs all associated
functions.
2. The DOM is now traversed in the opposite direction and thus the
functions are called in reverse order.
3. This reverse order guarantees that the functions of all
child elements have run by the time the function of the
parent element is run.
4. Once Angular has called the function of a directive, it
creates an instance element of the template element and
provides a scope for the instance.
5. So by the time the linking occurs, the instance element and scope
are already available and they are passed by Angular as
arguments to the function.

18.
1. Angular provides a way to run code before any of the child
element's functions have run;
2. Angular calls in the original order;
3. A function of an element is guaranteed to run before any
or function of any of its child elements.

19.
Use only to change the original DOM (template element) before
Angular creates an instance of it and before a scope is created.
Use to implement logic that runs when Angular has already
compiled the child elements, but before any of the child
element's and functions have been called.
Use to execute logic, knowing that all child elements have been
compiled and all and post-link functions of child
elements have been executed.

20.
The nitty-gritty of compile and link functions inside AngularJS directives

21.
Plunker link

22.
Angular Api Reference
ng-book
The nitty-gritty of compile and link functions inside
AngularJS directives