Window: screenX property
The Window.screenX
read-only property returns the
horizontal distance, in CSS pixels, of the left border of the user's browser viewport to
the left side of the screen.
Note: An alias of screenX
was implemented across modern
browsers in more recent times — Window.screenLeft
. This was originally
supported only in IE but was introduced everywhere due to popularity.
Value
A number equal to the number of CSS pixels from the left edge of the browser viewport to the left edge of the screen.
Examples
In our screenleft-screentop (source code) example, you'll see a canvas onto which has been drawn a circle. In this
example we are using Window.screenLeft
/Window.screenTop
plus Window.requestAnimationFrame()
to constantly redraw the circle in
the same physical position on the screen, even if the window position is moved.
js
initialLeft = window.screenLeft + canvasElem.offsetLeft;
initialTop = window.screenTop + canvasElem.offsetTop;
function positionElem() {
let newLeft = window.screenLeft + canvasElem.offsetLeft;
let newTop = window.screenTop + canvasElem.offsetTop;
let leftUpdate = initialLeft - newLeft;
let topUpdate = initialTop - newTop;
ctx.fillStyle = "rgb(0, 0, 0)";
ctx.fillRect(0, 0, width, height);
ctx.fillStyle = "rgb(0, 0, 255)";
ctx.beginPath();
ctx.arc(
leftUpdate + width / 2,
topUpdate + height / 2 + 35,
50,
degToRad(0),
degToRad(360),
false
);
ctx.fill();
pElem.textContent = `Window.screenLeft: ${window.screenLeft}, Window.screenTop: ${window.screenTop}`;
window.requestAnimationFrame(positionElem);
}
window.requestAnimationFrame(positionElem);
These work in exactly the same way as screenX
/screenY
.
Also in the code we include a snippet that detects whether screenLeft
is
supported, and if not, polyfills in screenLeft
/screenTop
using
screenX
/screenY
.
js
if (!window.screenLeft) {
window.screenLeft = window.screenX;
window.screenTop = window.screenY;
}
Specifications
Specification |
---|
CSSOM View Module # dom-window-screenx |
Browser compatibility
BCD tables only load in the browser