Why Does Updating Properties In One Object Change Another Object?

I'm loading JSON data into an object via ajax, copying that object to new objects (initData and newData). When I change the property of newData, the property of initData also chang

Solution 1:

It looks like data[prop] is an object (since you are later referring to newData.properties.Protein). Objects are always passed by reference, with the variable just being a pointer to it.

Since you're getting JSON in the first place, your object is JSON-able, so you can use that to "clone" the object:

$.getJSON(...,function(data) {
    initData = JSON.parse(JSON.stringify(data));
    newData = JSON.parse(JSON.stringify(data));
});

This will ensure that the objects are separate. There are other ways to do this, but this one avoids the manual recursion by using built-in methods (always faster)

Solution 2:

This sets both to reference the same memory space:

initData[prop] = data[prop];
newData[prop] = data[prop];

...so when you change newData, you also change initData. Instead of assigning by reference, you'll want to create a copy. I have to run, so I can't provide an example of that right now.