parsing JSON object in javascript and finding the depth

I am trying to find the depth of a node and I am not able to understand the below code. "node" is a node object passed as input.

 for (key in node) 
    {
        if (node.hasOwnProperty(key)) 
        {
            child = node[key];
            if (typeof child === 'object' && child !== null && key != 'parent') 
            {

This is what I have understood so far:

• Each node that is passed - we go through its properties
• For each property , the value of the property becomes a child
• if the type of child is an object and if the child is not equal to null and the property is not equal to the parent "node" that was passed. ( this part I dont understand)

Is my interpretation correct? Would appreciate any help. thanks!