Does the comma operator influence the execution context in Javascript?

Question

var a = 1;
var b = {
  a : 2,
  c : function () {
    console.log(this.a);
  }
};

b.c(); // logs 2
(b.c)(); // logs 2
(0, b.c)(); // logs 1

The fi

Answer 1

Refer to Indirect eval call, which gives more details about it.

 (     0        ,          b.c   )        (  )
     |____|   |_____|    |_____|
     Literal  Operator   Identifier

     |_________________________|
     Expression

  |______________________________|
  PrimaryExpression

  |______________________________|        |________|
  MemberExpression                        Arguments

  |________________________________________________|

  CallExpression

We can use the comma operator to fashion an indirect call to b.c which will force it to execute in the global context, the value of a is 1 in the global context.

Also the result of (b.c = b.c)() is 1

> (b.c = b.c)()
  1

Speaking in terms of ECMAScript, this is because both — comma operator (in (0, b.c) example) and = operator (in (b.c = b.c) example) perform GetValue on its operands.

Other indirect call formats as below

> (b.c, b.c)()
  1 
> (1? b.c: 0)()
  1
> (__ = b.c)()
  1