JS continuous assignment, pointer

There are many successive assignments in the JQ source code, similar to this:

var a = {N:1};  var B = A; Hold A to check back  a.x = a = {N:2};  alert (a.x);//  -undefined alert (b.x);/--[Object Object]  

There are many explanations on the Internet, here I do a record, the complexity of the simple, relatively easy to understand the process is this:

Give {N:1},{n:2} a name for the virtual object that actually holds the two memory addresses, such as: Obj1-"{n:1},obj2-" {N:2}

1) var a = {N:1}; Defines a pointer to an in-memory {N:1}, which is a = Obj1->{n:1}

2) var B = a;//defines b also points to the in-memory {N:1}, which is B = Obj1->{n:1}

3) a.x = {n:2};//Essence is obj1.x = {N:2}, which changes the objects pointed to by A and b

4) A = {n:2};//a pointer pointing to Obj2, is a new object

Now the result is:

A:A = Obj2 = {N:2};

B:b = Obj1 = {

N:1,

X:{n:2}

}

Well, here's the actual process, which is clearly written in the Web (http://snandy.iteye.com/blog/785445?page=2#comments) Comments:

A few simple excerpts:

1. Order of evaluation: from left to right

2, the Union of operators: right combination, but also from left to right evaluation

Main interpretation a.x = a = {N:2}; The order of execution of this sentence

According to the above two rules:

1) evaluation from left to right, that is, the first assignment to a.x that is a.x = expression

2) Read the a.x point at this point to who, at this point A to obj1-"{N:1}, that is, to obj1.x assignment into obj1.x = expression

3) Left Parse, enter "=" to the right, is an expression (A={n:2}), here is why not a bare a, that is why not the order a.x = A, mainly according to the second, right binding,

A = {N:2} is treated as a holistic resolution (the pointer to a is pointed to obj2) and the {N:2} is returned.

4) Assignment, obj1.x = Obj2 = {N:2}, 3rd step in the parsing process has a pointer to the OBJ2, so a.x (obj2.x) does not have this attribute, obj1 only

More difficult to understand is the third step, understand the points: first, not first calculate the right value (that is, not first calculate a = {N:2}), but first parse the left rule (pointer) a.x, parsed into obj1.x, before the beginning to the right,

At this time, according to the right binding, the (A={n:2}) as a whole, and then copy the calculation. Our awkward point is that a "a" in an expression points to a different object, as explained in the commentary. A appears several times, and can be seen as a recursive

JS continuous assignment, pointer