what is the DOJO

if you want  to create a WebGIS  you probably have heard the name of the arcgis javascript  api.

The ArcGIS Javascript API  is created by the esri developers. the Dojo is embede in the arcgis library.

so in this  tutorial i am going to show you  how to  add a reference to  the ArcGis javascript API.

there  are many sources  for getting dojo on the internet ...but  in my opinion the best one is  the esri server

the below lines of  codes show how to get  access to all functionality  of dojo and the ArcGIS Javascript  API

<link rel="stylesheet" href="https://js.arcgis.com/4.15/esri/themes/light/main.css"> <script src="https://js.arcgis.com/4.15/"></script>

ArcGIS javascript API..included  Dojo

you have to pay attention to when you have  a reference to the Arcgis JS API you also will have lasted version of DOJO

If you pay attention to these codes  you would find that I was going to use  the 4.15 version.This version of the library can load 3d maps  and do a lot of stuff on the 3d scene.

Although this capability  does not exist in the 3.x version  but many of the projects were implemented  by 3.x version and upgrading to 4.x version will have  some costs.

so 3.x version is still  a useful library for learning  and using in your project

let's coming back to our discussion.

At fist I want  to shw  you  an example  that  you probably have done  it  by the jquery.

Suppused  taht  you hame  an element on yor Html page  anf  you want  to get  InnerHtml  of  your  emelent

so  you have  to  get  ths  element  or  in the other  word  you have to  get  a refrence  to  this  element

<div id="div1">hello world</div>

below line  is  showing  that

  $(document).ready(function () {
           var InnerText= $("#div1").html()
                
   })

in this section after  loading page , we  are rady  to get inner  text  of the  an elemetn  which its id id 'div1'

Dojo  in very similar to pervious code

require(["dojo/dom"], function(dom){
    // fetch a node by id="someNode"
    var node = dom.byId("Div1");
});

here are many thing  that  you  have to know  before  diving  into dojo

the require function  in the  module loader  of  Dojo.it has 2 argument .number  one  is the  an Array  of modules  that  we  want to load  in project  and The nummber  two  is  a function

this function could  get  an  argument...each  argument  in this function will  be mapped  to  each  module  that is loaded  in the  require function.
For  example  in the  previous  sample  The dom argument that  has been passed  to  function will be a reference  to the  "dojo/dom"  module.

Dojo and  iquery  are  very  similar  to each other.so  learning  Dojo  will  not  be very hard  for  Jquery.programmers

here  i  should  say 

 best place for using Dojo is when you want to create a the web gis using the Arcgis Javascript API.

in the  next  articles i will  show  you  how to create  the Mosules  and  reusabale  code  in Dojo.

I hope you find this article is helpful