Demistifying Javascript Variables

The JavaScript variables are not easy as it seems to be.
In this shout I am trying to demystify few of them. Feel free to add if you have experienced similar behaviors which are hidden and not written explicitly.

• Reference or Value : Always wondered are JavaScript variables are references or values. let us go through some examples.
1. Scalar variables - Consider the snippet
   var s1 = "I am Einstein";
   var s2 = s1;
   console.log("1 :: S1=" + s1);
   console.log("1 :: S2=" + s2);
   
   s1 = "I am Newton";
   console.log("2 :: S1=" + s1);
   console.log("2 :: S2=" + s2);
   
   ... what do you think the output can be. Here it is.
   
   1 :: S1=I am Einstein
   
   1 :: S2=I am Einstein
   
   2 :: S1=I am Newton
   
   2 :: S2=I am Einstein
   
   
   So the conclusion here is the scalar types will always be kept as value.
2.  Array Types - consider the snippet
   var v1 = { "name" : "Tom", "skill" : "java"};
   var v2 = v1;
   console.log("1 :: v1=" + JSON.stringify(v1));
   console.log("1 :: v2=" + JSON.stringify(v2));
   
   v2.skill = "java, javascript";
   console.log("2 :: v1=" + JSON.stringify(v1));
   console.log("2 :: v2=" + JSON.stringify(v2));
   ... now do you think the output would change like previous one. Here it is.
   
   1 :: v1={"name":"Tom","skill":"java"}
   
   1 :: v2={"name":"Tom","skill":"java"}
   
   2 :: v1={"name":"Tom","skill":"java, javascript"}
   
   2 :: v2={"name":"Tom","skill":"java, javascript"}
   ... this is because JavaScript always keep the Object/JSON as refrences. And the statement "v2=v1" copy the references not the value unlike the previous case. After the any change in v1 would also change the v2 as they are pointing to the same object.
   
   
3. Vector Types (Object/JSON) - consider the snippet
   var a1 = ["Einstein","Newton"];
   var a2 = a1;
   console.log("1 :: a1=" + a1);
   console.log("1 :: a2=" + a2);
   ... here also the result is same as previous
   console.log("2 :: a1=" + a1); console.log("2 :: a2=" + a2);
   
   
• Associative Array: Javascript Associative arrays do not keep the ordering of the same. it depends on the hashing of the keys.
  var scientists  = { 2: "Einstein" ,  "1" :  "Newton" , 3: "Feynman"};
  console.log("1 :: scientists=" + JSON.stringify(scientists));
  var scientistsSorted  = {"S2":"Einstein" , "S1" : "Newton","S3": "Feynman"};
  console.log("2 :: scientists=" + JSON.stringify(scientistsSorted));
  ... see the output minutely,
  1 :: scientists={"1":"Newton","2":"Einstein","3":"Feynman"}
  
  2 :: scientists={"S2":"Einstein","S1":"Newton","S3":"Feynman"}
  

  ... what is going on, in case of #1, the hashing is done in an numeric way. So please be careful if you have an associative array with the keys as integer (even in form of a string), JavaScript will not be able to keep the ordering as you added. In order to avoid that you have prefix the keys with some character. see #2.