My changes in javascript file not reflecting in my plugin

I made change in Javascript file. Tried disabling plugin/re-activating/deleting javascript file and reuploading but nothing seems to upload the page as per my new javascript code.

Finally I went into view source and noticed the script src is set to "wp-content/plugins/my-plugin/js/my-plugin.js?ver=4.3.1"

If I type in this URL in the browser I get my old code back. However if I remove the query string at the end ?ver=4.3.1 it loads my new file code.

I am not sure who added ver=4.3.1. I don't have it in my plugin code. Could anybody please let me know how do I remove this and request my latest javascript code? It's been now more than a hour I am unable to fix this issue.

Many thanks!

via Chebli Mohamed