Is it possible to check the status of Scroll Lock, Num Lock and Caps Lock on page load of a web page? I've found ways to check after a keypress using JavaScript, but that's not what I'm asking.
No, you can't get system state from javascript. You will need them to type something and then analyze the input. Probably not what you wanted to hear =/
IN 2019, this is now possible:
var x = event.getModifierState("ScrollLock"); Source: https://www.w3schools.com/jsref/event_mouse_getmodifierstate.asp
来源：https://stackoverflow.com/questions/9060073/check-scroll-lock-num-lock-caps-lock-in-javascript-on-page-load