I want to display an indefinite progress bar while my JavaScript application performs some initialization, e.g. downloading a JSON object using the fetch api. Unfortunately, any activity freezes the progress bar on Firefox 52 64 Bit on Gnome 3.16.4, which may cause my users to reload as they assume the application crashed.
As an MWE I use many console.log calls to emulate the initialization, which also results in a blocked progress bar:
<html>
<head><meta charset="utf-8"></head>
<body style="width:99%;height:1000px;">
<progress style="width:99%;position:absolute;top:50%;height:20px;"></progress>
<script>
for(i=0;i<100000;i++) {console.log("nop");}
</script>
</body>
</html>
How can I achieve an unfrozen progress bar during activity?