CODEWITHSUNDEEP
javascript
user2550196
user2550196

Reputation: 43

Change the function context in JavaScript (for access local variables)

Is it possible to run a function in another context where it can access local variables with this context?

I made this proof of concept:

var t = (function()
{
    "use strict";
    var ab = 5;

    var f = (function(t)
    {
        return function(c){ c.call(t); }
    })(t);

    return f;

})();

t(function()
{
    return ab;
});

This give me this error: ReferenceError: ab is not defined

Is there a way that the anonymous function that I pass to t can access the local variable ab?

Upvotes: 3

Views: 351

Answers (1)

jAndy
jAndy

Reputation: 236022

Unfortunately (or fortunately) you can't do that. The problem which arises here is that you cannot "pass around" the such called Activation Object from a function (context). Function.prototype.apply and .call can only provide an option to set the context for a function from any regular Javascript Object, but formal parameter, function declarations and variables are not stored in any "regular" object. These values are hold in the Scope chain underneath and are stored in the such called Activation Object (or Lexical Environment Record) which you cannot access directly from Javascript.

Upvotes: 2

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