When the webpage loads I am running this code:

for(let i = 0; i < count;) {
    
    ...
    
    if(condition) {
        //draw with canvas api
        ++i
    }
}

It's a potentially infinite while/for loop that draws some art.

If I keep the art variables reasonable, then the piece finishes and the loop exists. But sometimes it could take several minutes or potentially run forever.

The problem is, when this is happening the browser can't accept any user input. So, there's no way for the user to halt the algorithm, eg. with a button.

How can I receive user input while running this loop?