I have a simple doubt that when we specify window.clientheight in JavaScript for mobile screens, does it tells the whole screen's height including navigation panel (shown in image) or it excludes that panel.

And if it includes that panel (as I'm guessing), how can I specify only screen's width excluding the panel.
in your senerio, window.innerHeight is better option for you. I guess.
console.log(window.innerHeight)
clientHeight belongs to an element and window is not an element. So there is nothing for window.clientHeight.
window.clientHeight = undefined
read this, this may help you : https://javascript.info/size-and-scroll-window