Window.screenLeft

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Window.screenLeft read-only property returns the horizontal distance, in CSS pixels, from the left border of the user's browser viewport to the left side of the screen.

注意 : screenLeft is an alias of the older Window.screenX 特性。 screenLeft was originally supported only in IE but was introduced everywhere due to popularity.

句法

leftWindowPos = window.screenLeft

A number equal to the number of CSS pixels from the left edge of the browser viewport to the left edge of the screen.

范例

In our screenleft-screentop example, you'll see a canvas onto which has been drawn a circle. In this example we are using screenLeft / screenTop plus Window.requestAnimationFrame() to constantly redraw the circle in the same physical position on the screen, even if the window position is moved.

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);

Also in the code we include a snippet that detects whether screenLeft is supported, and if not, polyfills in screenLeft / screenTop 使用 Window.screenX / Window.screenY .

if(!window.screenLeft) {
  window.screenLeft = window.screenX;
  window.screenTop = window.screenY;
}

规范

规范	状态	注释
CSSOM (CSS 对象模型) 视图模块 The definition of 'Window.screenLeft' in that specification.	工作草案	初始定义。

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`screenLeft`	Chrome Yes	Edge 12	Firefox 64	IE Yes	Opera Yes	Safari Yes	WebView Android Yes	Chrome Android Yes	Firefox Android 64	Opera Android Yes	Safari iOS Yes	Samsung Internet Android Yes

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