NodeList and array of coarse dim sum

In JS, through document.getElementsByTagName ("tag"), get a NodeList object, for this NodeList object we can use subscript way to access, It is easy to use the NodeList object as an array or in an array to be used as an NodeList object, and then call the NodeList method, which should be taken precautions.

This time I made one of these mistakes.

I used loops to create a bunch of IMG elements, and then I put those elements into an array, and then I used this array to invoke the NodeList method, InsertBefore (), but there was an error.

Reason:

<div>
  
  
</div>

As the figure shows, this is the difference between the two, arr[0 in nodelist] always points to the first IMG in the node tree, because NodeList is dynamically changing.