Question

I have the following source code.

testObj = {}

function testFun()
{
    this.name = "hi";   
}

function test () {

    var instanceOfTestFun = new testFun();

    testObj.pointerToFun = instanceOfTestFun;

    instanceOfTestFun = null;

    console.log(testObj);

}

$(document).ready(test);

I expected to see ‘null’ for the console output of testObj, but I see testFun function. I thought javascript uses ‘pass by ref’ for objects.

Please…advise me…

Answer 1

testObj.pointerToFun and instanceOfTestFun are two references to the same object.

When you write instanceOfTestFun = null, you’re changing instanceOfTestFun to point to nothing.
This does not affect testObj.pointerToFun, which still refers to the original object.

If you change the original object (eg, instanceOfTestFun.name = "bye"), you will see the change through both accessors, since they both point to the (now-changed) object.