I think you must use onchange, not onChange
el[j] = document.createElement('input');
el[j].type = 'file';
Attaching Event Handlers in OOP
The simplest way to attach event handlers into your page is to insert them directly as attributes on the HTML tags of the object that will trigger them. To trigger an event handler so attached requires that the particular action that the event handler recognises be performed in relation to the object to which it is attached.
In general event handlers will be attached into a tag using code similar to the following (substituting the appropriate event name and function to run for the code in italics):
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Thanks and share your thoughts.