Accessing function return value through nested object inside IIFE

Question

I'm trying to set an object value to a function call using another value (array) as its parameter, however, for some reason the value comes back as undefined, I'm then trying access that value right after that. It's inside an IIFE.

I am unsure why this is happening because to the best of my knowledge the scoping is okay and the value should be initialized and executed by that time?

Here's a simplified example:

(function(){
 var minefield = [1,2,3,'M',4,5,6];

function findMachine(minefieldMachine) {
  return minefieldMachine === 'M';
}

  var terrain = {

    start:{initialMachienLocation:minefield.findIndex(findMachine)}, 
    currentMutable:{mutableIndex:terrain.start.initialMachineLocation}//Error: "Uncaught type error cannot read property 'start' of undefined"
//Why isn't the above accessing the value declared in terrain.start.initialMachineLocation through the function call?

  }
}());

However, doing this works, out of context from above:

function findMachine(minefield){return minefield === 'M'}
[1,2,3,'M',4,5,6].findIndex(findMachine);
//above returns the proper index value, 3.

you cant access to any function or var inside, seems is private... — Álvaro Touzón
– Álvaro Touzón, Commented Nov 16, 2017 at 18:57

Quentin · Accepted Answer · 2017-11-16 19:03:10Z

3

This has nothing to do with the function.

What you are attempting to do is, essentially, this:

var foo = {
    a: 1,
    b: foo.a
}

You need to consider the order of operations.

The object literal constructs an object which is then assigned to the variable foo.

… except that while the object is being constructed, you are trying to read the value of foo. It doesn't have one yet, so this fails.

You need to do this in two steps.

var foo = {
    a: 1,
}
foo.b = foo.a;

answered Nov 16, 2017 at 19:03

Quentin

949k136 gold badges1.3k silver badges1.4k bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Accessing function return value through nested object inside IIFE

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related