How to calling the button when timer control time count zero

JavaScript timing methods automate a particular task to be done on the fly without you having to click a button or call an event.JavaScript stop watch or rather stop down timer can be implemented using the JavaScript timing methods which are executed in time intervals.

 

JavaScript timing is made up of two key methods:

example:

var setTime = setTimeout( function ( ) { // javascript statements }, 500 );

Or

var setTime = setTimeout( "setTimeFunction( )", 500 );

clearTimeout( return ID of setTimeout() );

 

to create a stopwatch referred this link

https://www.ostraining.com/blog/coding/stopwatch/