How Does JavaScript's `delete` Operator Actually Work on Objects?

Demystifying Object Deletion in JavaScript

JavaScript's delete operator baffles many developers, especially regarding its limited impact on objects. Contrary to expectations, the delete operator merely removes references to objects, leaving the actual objects untouched in memory.

To illustrate this concept, consider the following code snippet:

var obj = {
    helloText: "Hello World!"
};

var foo = obj;

delete obj;

After executing this code in Safari 4, the variable obj becomes null, but foo continues to point to the same object as before. This occurs because JavaScript's delete operator targets only references, not the underlying objects themselves.

The rationale behind this behavior lies in garbage collection. JavaScript utilizes a "retain/release" basis for garbage collection, implying that objects are reclaimed only when there are no more references pointing to them. Thus, deleting obj simply removes that particular reference, leaving any other references untouched.

Hence, the object remains in memory because foo still points to it. Deleting obj solely eliminates one path to access the object, not the object itself. In essence, JavaScript's garbage collector handles the deletion of unused objects, thus eliminating the need for manual deletion.

However, deleting references can benefit the garbage collector. By removing unused references, the collector can better identify objects ready for reclamation. Large objects with lingering references may otherwise remain uncleared, impacting memory usage even if they are no longer required by the program. As a result, deleting references can assist the garbage collector in optimizing memory management.

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