Update previously undefined variable for asynchronous callback function in JavaScript

Asked Feb 06 '19 at 16:46

Active Feb 06 '19 at 16:53

Viewed 16 times

Let's have a look at this short JavaScript snippet:

function _function(param1, param2) {
  console.log(param1 + " and " + param2);
}

function test(callback) {
  var i = 0;
  var j = undefined;
  var test = setTimeout(callback.bind(null, i, j), 1000);
  i = 1;
  j = 2;
}

test(_function);

Now it works as expected: console.log is going to display

0 and undefined

Is it possible to only update j (here: to 2) while keeping i equal to 0 within _functions's scope and without using j as a global variable ?

edited Feb 06 '19 at 16:53

Heretic Monkey

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asked Feb 06 '19 at 16:46

user1511417

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function calls are pass-by-value, not pass by reference. – Patrick Roberts Feb 06 '19 at 16:53
Alter your `test` function to take `j` as an argument, then you could just call `test(_function, 2)`. It's not clear why you would want it to work the way you're asking. – Heretic Monkey Feb 06 '19 at 16:58

Update previously undefined variable for asynchronous callback function in JavaScript

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