Running javascript in Chrome console runs twice sometimes, why?

Question

this code takes some values from a page, compares them and presses a button if true, and it does that in a loop

Running this pice of javascript in chrome console works fine for some time and then it runs two time. The script works fine with a compiler so why does it sometimes do that in Chrome console? And is there a way to execute the code just once all the time, without taking out setInterval or setTimeout or if, as I absolutely need them!

 setInterval(function() { var time = document.getElementById("timer").innerHTML;; if(time>0){ setTimeout(function() { var x2b = document.getElementById("2x").innerHTML; var x3b = document.getElementById("3x").innerHTML; var evt = document.createEvent("MouseEvents"); if (x3b< x2b) { evt.initMouseEvent("click", true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null); var run = document.getElementById("3x"); run.dispatchEvent(evt);} }, time);} }, 2000); 

Answer 1

Probably a problem with your code and not Chrome.

How does #timer get updated? If it's value happens to be something like 2500 then the setTimeout will be placed on the call stack. Then 2000ms later the next interval will occur. If #timer happens to be something like 500 at that time then another setTimeout will be placed on the call stack. After another 500ms both of the timeouts will be triggered, one right after another. This may make it appear that the timeout is occurring twice.

It would be helpful to record the current time ( Date.now() ) and what the value of #timer is, and log that info when the timeout occurs.