Browser on my mobile phone gives strange value for these properties when <meta name="viewport" content="width=device-width> is not set:

alert(document.documentElement.clientWidth); // 360
alert(document.documentElement.clientHeight); // 1932

Here are all the values:

// mobile with <meta name="viewport" content="width=device-width>
document.documentElement.clientWidth: 360
document.documentElement.clientHeight: 710
window.innerWidth: 360
window.innerHeight: 710

and

// mobile without viewport
document.documentElement.clientWidth: 360
document.documentElement.clientHeight: 1932
window.innerWidth: 980
window.innerHeight: 1933

I thought that document.documentElement.clientWidth and document.documentElement.clientHeight are used to get viewport size without scrollbar if present and window.innerWidth and window.innerHeight are used to get viewport size with scrollbar if present.
Does anybody know why document.documentElement.clientWidth and document.documentElement.clientHeight has such strange values on mobile when viewport is not set?