The progress bar is updated only after the end of the cycle. Help, please!

I added to the bar element, the Progressbar. It works, all is well.

One of the functions has a loop, like

for (var i=0;i<myArray.length;i++) {

myProgressBar.value = (i+1)*(100/myArray.length);

}

When the panel is opened and script is executed, the value of the progress bar is zero after the loop ends, the value of the progress bar from 100.

I also tried adding alert(""); for each iteration of the loop, then the value of the progress bar with each step of the cycle is updated. What could be wrong?

1. Thank You!