JavaScript: flatten an array without using reduce library

Question

I have a nested array named $scope.instruments, its contents are:

collapsed:

expanded:

I also have an object:

This object contains 2 arrays: AttributeID and SPAttributeRefID.

Currently I am flattening the $scope.instruments array using reduce function:

$scope.instruments = $scope.instruments.reduce(function (result, instrument) {
    result[instrument.ID] = instrument;
    return result
}, {});

Then I access the AttributeID of the object and assign it to a variable like this:

$scope.recordInstrument = $scope.instruments[data.AttributeID[0]].ID;

I would rather use a different method to obtain the same result. I read that an array can be flatten using a for loop, that it is a more efficient method of doing it. Unfortunately, what I have tried so far, is not giving me the same results.

var arrInstruments = $scope.instruments;
var arrLength = arrInstruments.length;

for (var i = 0; i < arrLength; i++) {
    console.log(arrInstruments[i]);                                
}

Can someone give me a hand converting the code that uses the reduce function to use a loop and have the same result in the assignment of AttributeID?

Many thanks.

reduce is not a library and not inefficient either. Why not just use your working solution? — Bergi
– Bergi, Commented Oct 10, 2016 at 18:09
Your screenshots don't show a nested array. You seem to be confused by the console representation of large arrays. There is no need to flatten anything here (but notice that your reduce code isn't even flattening anything either, rather it is building an ID lookup table). — Bergi
– Bergi, Commented Oct 10, 2016 at 18:10
You're not flattening, you're really creating a new object with the values from the original array. I agree with Bergi, keep what you have. — adeneo
– adeneo, Commented Oct 10, 2016 at 18:12
I understand, and I am ok keeping the in place solution. The problem I am having I explained in a different question, but I have not been able to get much help to correct it. Here is the link: stackoverflow.com/questions/39962933/… — erasmo carlos
– erasmo carlos, Commented Oct 10, 2016 at 18:13

Dekel · Accepted Answer · 2016-10-10 18:12:23Z

3

This code should do what you are looking for:

var arrInstruments = $scope.instruments;
var arrLength = arrInstruments.length;
var result = {}
for (var i = 0; i < arrLength; i++) {
    result[arrInstruments[i].ID] = arrInstruments[i];
}
// the result variable contains what you want.

However I really don't understand why you would want that.

This screenshot you took:

Is not a multidimensional array. It's only the way your console show you a very large array (so it will not need to "draw" everything).

answered Oct 10, 2016 at 18:12

Dekel

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4 Comments

erasmo carlos Over a year ago

Thank you Dekel. How can by using that loop, do an assignment like the one on my original code: $scope.recordInstrument = $scope.instruments[data.AttributeID[0]].ID;

Dekel Over a year ago

I'm sorry but I'm not so sure I understand the question.

erasmo carlos Over a year ago

I understand that the console puts the array that way because it is too long. I am trying to set the value of a drop down menu. $scope.newpage is the record. $scope.instruments are all the values that populate the dropdown menu. When the record enters edit mode, I need to use the record's AttributeID value, to set the $scope.instruments array.

erasmo carlos Over a year ago

Never mind. I got it now. I did: $scope.recordInstrument = result[$scope.newpage.AttributeID[0]].ID;

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