JavaScript - Replacing array value within object

Question

I'm trying to write a function that normalizes features (between 0 and 1) in a dataset. I want to iterate through all the features and replace values as I normalize them. Normalization works well, but I'm unable to overwrite the previous value.

Data.prototype.normalize = function(dataset) {

    // Get the extent for each feature
    for (var feature = 0; feature < this.featureCount; feature++) {
        var extent = this.getExtent(feature, dataset),
            min    = extent[0],
            max    = extent[1];

        // uses extent to normalize feature for all companies
        for (var company = 0; company < this.companies.length; company++) {
            var value      = this.companies[company][dataset][feature],
                normalized = this.normalizeValue(value, min, max);

            value = normalized;
        }
    }

}

It all fails at

value = normalized;

If I console.log(value) after overwriting it everything seems to work, but only within the scope of the function. Outside of this scope the original value remains.

data.companies[n] = { features : [1, 2, 3, 4, 5], other properties... }

Here is an example of the feature array within my main object.

Any thoughts on how to fix this?

Thank you!

Primitive types are never passed by reference in Javascript. — Tomalak
– Tomalak, Commented Nov 28, 2017 at 21:09

Christian Santos · Accepted Answer · 2017-11-28 20:59:48Z

5

In order for the change to be reflected in your object as opposed to the function, you need to explicitly set the property of your object.

Modify your for loop to explicitly set the normalized value like so:

for (var company = 0; company < this.companies.length; company++) {
    var value      = this.companies[company][dataset][feature],
        normalized = this.normalizeValue(value, min, max);

    this.companies[company][dataset][feature] = normalized; // explicitly set value
}

answered Nov 28, 2017 at 20:59

Christian Santos

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1 Comment

Tomalak Over a year ago

Nice psychic debugging.

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