Javascript variable acts like reference instead of object

Question

I have an issue I can't quite put my finger on.

var records = dataView.getItems();

for (var i = 0; i < records.length; i++) {
    var date = records[i].RecordCreated;
    records[i].RecordCreated = new Date(parseInt(date.replace('/Date(', '')));
}

records = JSON.stringify(records);

This is a small loop that takes existing data from a SlickGrid dataview and converts the /Date(###)/ format to a proper date format in order to be deserialized on the server. This works fine.

The weird issue is that the var records = dataView.getItems(); definition is acting more like a reference than an individual, unique, object. Consider the following code:

var records = dataView.getItems();

// Debug Code [A]
console.log(records);
console.log(dataView.getItems());

for (var i = 0; i < records.length; i++) {
    var date = records[i].RecordCreated;
    records[i].RecordCreated = new Date(parseInt(date.replace('/Date(', '')));
}

// Debug Code [B]
console.log(records);
console.log(dataView.getItems());

records = JSON.stringify(records);

The console logs at [B] are both identical, where one would expect them to be different. Meaning instead of seeing the second log with unchanged /Date(###)/ format dates, proper date objects are printing.

Even stranger is that at [A] the console logs are printing as if the loop ran asynchronously and finished prior to the console.log() command was called.

This is all wrapped in a function with some conditional statements to do different loops, nothing crazy. What I need to know is how/why the records definition is not working as per usual (a unique variable in memory, that can be edited without affecting the original object).

Solution

---

So the problem was that records was receiving the original object from the SlickGrid library. What I did to fix the issue was clone the object before assigning it to records.

Clone function:

function clone(obj) {
    if (obj == null || typeof (obj) != 'object')
        return obj;
    var temp = new obj.constructor();
    for (var key in obj)
        temp[key] = clone(obj[key]);
    return temp;
}

Usage:

var __data = dataView.getItems();
records = clone(__data);

Hope this helps anybody else viewing this question in the future.

Answer 1

looks like your records variable is an array being returned from dataView.getItems(). This variable IS a reference to the array object, so changing things on that object will be reflected in all the references to the object.

Answer 2

You should ensure that dataView.getItems() calls Array.protototype.slice on any collection it is returning