node.js/javascript: trying to set variable equal to the value returned by a function

Question

> var score = 6;

> function test(callback) {
    var score0 = 16;
    console.log(score0);
    function callback() { return score0; }; 
    callback();
  }

> score = test()
    16

> score
    undefined

The appropriate value for score should be undefined. What should I be doing?

You're missing return statement in your test() function. return callback(); will do the job. — halfzebra
– halfzebra, Commented Oct 26, 2015 at 12:26

Majid Yaghouti · Accepted Answer · 2015-10-26 12:29:30Z

1

Change the last line of test() to:

return callback();

answered Oct 26, 2015 at 12:29

Majid Yaghouti

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1 Comment

Vietnhi Phuvan Over a year ago

Thanks, I got killed at a hackathon over this :)

Vietnhi Phuvan · Accepted Answer · 2015-10-29 18:39:53Z

0

Here is one way to have a callback return a value:

function tens(value, callback) {
   return callback(10*value)
}

var n = tens(100, function(result){ return result })

n
  1000

Here is another way:

function tens(value, callback) {
   return callback(10*value)
}

var n = tens(150,
  function(err, result) {
    if (err) throw err
    else return result
  })

n
 1500

The trouble with the way I posed the question is that

function test() {
   var score0 = 16;
   return score0;
}

would have worked just as well. And if this simplified syntax works just as well, then the function "callback" in my original question is not a callback function but a function that I called by coincidence "callback"

answered Oct 29, 2015 at 18:39

Vietnhi Phuvan

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