Javascript multiple assignment clarification?

Looking at var a=b=1; , I already know that both a and b has the same value.

But my question is :

Does the a gets its value from 1 or from b ?

I made a small test :

/*1*/   (function (){
/*2*/     var j = window.j = function (){ alert('3');};
/*3*/     window.j2 = j;
/*4*/   })();
/*5*/   
/*6*/   window.j(); //3
/*7*/   window.j=null;
/*8*/   window.j2();//3

As you can see line #8 yields 3 so I persume that a is not having the value of b but the value of 1 .

Am I right ?

visualize :

(function (){
  var j = window.j = function (){ alert('3');};
      |
      |          ^        ^
      |          |        |            //which one ?
      +----------+--------+  
})();

---

Assignment in javascript works from right to left. So you are getting your value from window.j . Re-setting window.j will not affect the result because Javascript variables always passes by value, exception is array or object.

Example of passing value by ref in JS object:

var obj = { x: 2 };
var anotherObj = obj;
anotherObj.x++;
alert(obj.x); //3 

You can find more information here.

More useful examples available in this answer.

---

The "=" operator associates to the right so "a=b=1" is equivalent to "a=(b=1)". So 1 is assigned to b first with a result of 1, which is then assigned to a.

---

Assigment in JavaScript is right associative, so you are correct. In

a = b = c;

a takes the value of b at time of assignment, so if b is later assigned to something else, a retains its value (which happens to be the same as c )

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